new evidence. federal agents zero in on how the marathon bombings were carried out, but who's to blame and what their motive was remains a mystery. amid heightened security in washington, a mississippi senator is a possible target of an attack with deadly poison. and britain says good-bye to its iron lady. world leaders gather for margaret thatcher's funeral. captioning funded by cbs captioning funded by cbs this is the "cbs morning news" for wednesday, april 17th, 2013. good morning. good to be with you. i'm anne-marie green. well, investigators are zeroing in on what caused the explosions at the boston marathon that killed three people and injured more than 170 others. while they are urging the public to help them find who planted

those two bombs, last night the victims were remembered. susan mcginnis is in boston with the latest. susan, good morning. >> reporter: good morning, anne-marie. investigators working with thousands of tips say they believe both bombs were hidden in back packs inside pressure cookers and constructed in such al way as to cause maximum death and injury. fbi photos show remnants of what they believe is a pressure cooking used as a bomb casing in the boston marathon explosions. when used as a bomb, pressure cookers briefly contain the explosion, magnifying the power of the device. >> there has been some debris recovered from some of the rooftops nearby as well as some of the debris has been embedded in some of the buildings nearby. so that gives you a scope of the power of the blast. >> reporter: they also filled the pot with bbs and nails

in order to injure as many people as possible. it worked. the shrapnel tore through limbs forcing doctors to perform several amputations. >> almost all of them had such severe trauma in their lower extremities that it was just beyond salvation. we just completed what the bomb had done. >> reporter: while the investigation continues, victims are being remembered through makeshift memorials like this one through the marathon cows and through candlelight vigils. about a thousand people gathered in dorchester, massachusetts, to remember 8-year-old martin richard. he was the youngest victim. >> i have an 8-year-old son myself who was out there that day right before it happened. i sympathize for the parents that are going through sch a situation. >> reporter: 29-year-old krystle campbell was also killed. her mother is still in shock. >> i can't believe this has happened. >> reporter: the third person killed was a boston university grad student. and president obama will come here tomorrow.

he'll speak at an interfaith service dedicated to those killed and injured. anne-marie? >> susan mcginnis in boston. thank you, susan. well, earlier i spoke with cnn correspondent john miller. he's also a former assistant fbi director and he says the bombs were simple but deadly. >> what we're learning is that both devices, the one in front of the runner's shop and the lenscrafters, the one in front of the starbucks were pressure cooker devices contained in black nylon bags or more likely backpacks, and the way the pressure cooker works is you put your explosives inside. it's a good device. for high explosives you can use smokeless powder or pyro techs, smokeless powder and you have your timer, your initiator, and when it's supposed to detonate. it detonates inside and then the pressure of the explosion builds up within the pressure cooker

until it breaks. so what the pressure cooker does is it contains that explosive energy till it can't anymore, and then it in and of itself becomes shrapnel and lets that explosive energy out at a much higher rate because it's built up inside. and if you take that shrapnel as we've seen in so many cases and tape on the outside, you have nails and nuts and bolts flying at people at 1,500 feet per second. >> shrapnel and other fragments are being analyzed at the fbi lab in quantico, virginia. well, the response to help victims was quick and that was in part due to the number of doctors and nurses already stationed at the finish line. elaine quijano spoke with one of the doctors. >> reporter: dr. john pazuto was one of the volunteers with the

national armory. he was treati ining someone wit foot injuries. >> people were running all over. when he said, that's definitely a bomb, we responded. >> reporter: almost everyone in the tent rushed to the wounded. >> that's what changed me. that five minutes i was at the finish line to see the sidewalk that was now blood red literally everywhere. >> reporter: what did it sound like? >> a lot of orders being given. not a lot of panic. i mean the nurses, the doctors, they were -- like they were ready for this. they knew what to do. >> reporter: the bandaged injuries of one man are unforgettable. >> he came in in a wheelchair with a turn continue on his right leg and basically his tibia leg or tibia with nothing around it, no skin, no foot, no leg. >> reporter: what goes through a doctor's mind when you witnessed the carnage that you witnessed? >> at the time, i don't think you think about that. i think you just try to help the people. its like police and fire and physicians. you try to help people who need help.

>> reporter: but what sticks most in his mind is this woman he treated and the last thing she asked him before she left. >> what's your name. and you tell them your name and you get choked up. you're giving them your name and now they want to thank you and you think, this is real. >> reporter: it's estimated about half of those severely wounded survive because dozens of doctors and nurses were already on hand and able to quickly triage the wounded. elaine quijano, cbs news, boston. investigators may have a suspect in connection with the mailing of ricin, a deadly poison, to mississippi senator roger wicker. the envelope was intercepted at a mail facility and quarantined. testing showed it contained ricin. the envelope had a memphis post mark but no return address. it did not reach wicker's office. investigators give gave no

indication why the letter was sent to him. and the senate is expected to vote today on gun control legislation. there were weekend rallies across the nation in support of tighter gun control. it would expand background checks. it would also tighten laws against gun trafficking. and a funeral will be held this morning in london for former prime minister margaret thatcher. leaders from 170 countries are attending. mark phillips is at st. paul's cathedral in london. mark, good morning. >> reporter: good morning, anne-marie. well, this was always going to be a tense affair, this funeral for margaret thatcher. after the events this week in boston, the concerns have been ratcheted up even higher. it comes from two sources. she was a very divisive figure and the fear is the strength of opinion, particularly in opposition to her and her policies could mar this funeral as well. protests are planned. the question is whether they will be peaceful or otherwise. but there's also a terrorist threat as well.

this is the first major street event if you will in the world since boston. the queen will be here. it will be populated as well by many dignitaries as you say from around the world. it's a tempting target. and there are two potential terrorist sources, one being the usual suspects in the middle east, the other being irish dissident republicans who you may recall once tried to kill her when she was alive. nobody knows quite what they might or might not have planned for this. the security response has been massive. the root of the funeral cortege will be lined by service purse nell, some for ceremonial reasons, others for security. and london police have been brought in from around the country. more than 4,000 police officers will be on duty here trying to keep the peace. so a day of reverence but also one of great concern. anne-marie? >> indeed. mark phillips in london, thank you. coming up on the "morning news," flight fallout. american airlines scrambles

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far as dubai to sway. and there are new threats from north korea aimed at the south. the north's army said tuesday it would retaliate without any notice. pyongyang promised, quote, sledgehammer blows, if they don't apologize for blows on monday. that's when the north celebrated the birthday of its founding leader. well, on the "cbs moneywatch" now, turbulence for american airlines and the high cost of owning a car. erica ferrari is here in new york with that and more. good morning, erica. >> good morning, anne-marie. songs in japan were mostly high owner a weaker yen. tokyo's nikkei rose 1%. hong kong's hang seng sank half a percent. there was a rebound on wall street thanks to strong housing and corporate around earnings reports. the dow jumped nearly 158 points while the nasdaq closed up 48. american airlines warn s passengers traveling today there

may be a computer meltdown. keeping the carriers planes on ground and stranding thousands. american fixed the problem by mid afternoon but some passengers might still encounter canceled and delayed flights. j more signs of recovery as builders started work on a million new homes in march. that hasn't happened since june 2008 and was fueled by a surge in apartment building construction. single-family home construction, however, fell by nearly 5%. the international monetary fund now predicts the global economy will grow by 3.3% this year, down 0.2 of a point since its january forecast. the imf says the u.s. economy will expand by a slightly smaller 1.9% while eurozone economies will swing slightly. car ownership comes with its own expenses, and it's a lot more than you probably realize. a new report out by aaa found

that owning an average sedan will drain you over a thousand when you factor in gas, main tense, and tires. that cost is up about 2% from last year mostly because of an 11% surge in maintenance costs. anne-marie? >> erica ferrari here in new york. thanks, erica. straight ahead, your morning weather. plus, in sports, the voice of the nfl goes silent. we will remember legendary broadcaster pat summerall. legendary broadcaster pat summerall. want to give your family more vitamins, omega 3s, and less saturated fat? it's eb. eggland's best eggs. better taste. better nutrition. better eggs. it's eb. for those nights when it's more than a bad dream, be ready. for the times you need

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here's look at today's forecast in some cities toward country. new york, expect morning showers. nothing but sunshine in miami. rain in chicago, 55 degrees the high there. dallas, thunderstorms, and los angeles, sunshine, 74. >> and time now for a check of the national forecast. another major snowstorm is bringing up to 18 inches to wyoming and a foot to colorado as it moves into the upper midwest where a foot could fall by thursday. the same storm also brings the risk of severe thunderstorms in the region. expect scattered thunderstorms in tennessee, carolinas, and georgia, and the northeast is mostly dry. in sports now we begin with sad news. hall of fame broadcaster pat summerall died yesterday of cardiac arrest. his style was simple, to the point, and usually flawless. for more than four decades summerall broadcast some of the biggest sporting events of the time.

but as reported when you heard his deep voice, you thought of only one thing. football. >> good afternoon. i'm pat summerall here along with john madden. >> reporter: he was a welcome presence in our living room every sunday for more than four decades. >> no time on the clock and the patriots have won super bowl xxxvi. unbelievable. >> reporter: summer awl did more than just broadcast game. he also played in the nfl for ten years. >> it was a tough transition because you missed the thrill of playing. you get over it pretty quickly, though, when you realize the excitement of broadcasting. it comes very close to being a player, except you don't get hit. >> reporter: summerall checked into the betty ford clinic in 1992. he reflected on his football career and his drinking days. >> the football part of it, yes, i'd go back and do it again. i don't know that i'd go back and do the rest of it. i think i'd take better care of myself. >> reporter: in a 2004 interview

in his home the broadcaster told me he was most proud of overcoming his personal battles. that allowed him to reconcile his relationship with his estranged children. >> i think number one, becoming a christian, letting them know i had become a christian, letting them know what i believed probably thought of as the chasm to be smaller. the fact that that whole chasm has been wiped out, we're father and son, father and daughter again, i think that's the thing i'm most proud of. >> pat summerall was 82 years old. in baseball the victims of the marathon bombing were remembered throughout the major leagues. ♪ sweet caroline >> the yankees were one of several clubs that played fenway park's favorite "sweet caroline."

the atlanta braves hit five home runs including three in the eighth inning to beat the kansas city royals, 6-3. it was the braves' tenth consecutive win and their best start in 19 years. >> in oakland rick ankiel tried to make a catch. ankiel missed and josh reddick scored the winning run. the a's beat the astros, 4-3. when we return, another look at this morning's top stories, and answering a longstanding call to overhaul immigration. senators unveil details of bipartisan legislation. at break, i need all the help i can get. that's why i like nutella. mom, what's the capital of west virginia? charleston. nutella is a delicious hazelnut spread my whole family loves. mom, have you seen my -- backpack? nutella goes great on whole-wheat toast or whole-grain waffles. and its great taste comes from a unique combination of simple ingredients like hazelnuts, skim milk and a hint of cocoa. yeah, bye. have you seen my -- yes. and...thank you.

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,,,, here's a look at today's forecast in some cities around the country. occasional thunderstorms in washington, d.c. thunderstorms also in atlanta and showers in st. louis. snow in denver. afternoon showers in seattle. here's another look at this morning's top stories.

investigators say kitchen pressure cookers loaded with explosives, nails, and ball bearings were used in the deadly boston marathon bombings. the fbi is urging the public to bring them pictures or video that may help them find a suspect in the attack. and the senate is expected to vote on gun control today. weekend rallies urged an end to gun violence. the measure to be voted on today would expand background checks. the senate is expected to hold hearings this week on a sweeping new immigration bill. republican senator john mccain and democratic senator chuck schumer outlined the bill to president obama tuesday. the legislation drafted by four democrats and four republicans would provide a 13-year path to citizenship for illegal immigrants in this country. it would also create new visa programs for skilled workers. and they say parting is such sweet sorrow. an airport worker delivered his

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the boston marathon bombings injured 176 the boston marathon bombings injured 176 people, 17 of them critically. doctors believe many lives were saved because the victims were treated by medical teams at the finish line there to help runners, and some of the best hospitals in the world were nearby. scott pelley spoke with doctors at brigham and women's hospital. >> reporter: brigham & women's is five minutes by ambulance from the scene of the attack. among those in the emergency department were trauma surgeon joakim hagganhaggans. john walls and trauma surgeon dr. zara cooper. >> there were two things going through my head. one was actual fear, just myself, because i hadn't been in such a situation like this

before and i really did feel like it was a war zone in some ways, and then another feeling was reassurance because i think everybody really pulled together in a very remarkable way. >> the patients you treated, what did you see? >> significant amount of burns, second and third degree burns as well as penetrated trauma of shrapnel to the face and neck and to the upper extremities. there were traumatic amputations from the blasts, some very sick patients that needed help. >> then there were three patients, i think three in total who obviously had planted their shrapnel as part of their device. small two to three-millimeter types of okay objects like bbs and carpenter nails. >> nails and ball bearings, bbs that you believe were part of the bomb itself. >> they wouldn't be out there anywhere unless they were part of the device. >> reporter: >> there have been a lot of

advances in acute trauma care on the battlefield over these last ten years. did any of that come into play in the emergency department yesterday? >> absolutely. in fact, the conflicts in iraq and afghanistan have taught us an incredible amount about how to manage wounds like this. >> the patients you received, a lot of them had first aid right there at the finish line of the race. did that save some of the people? >> absolutely. >> we had patients arrive with tourniquets in place which most certainly would have saved their lives from bleeding to death. >> without tourniquets some of these patients could have bled to death before they even reached the emergency department. >> absolutely. >> anything else that compares to this? >> the last time i saw anything near this was 9/11. we were told to prepare the hospital for an influx of burn patients, and then we all waited for many hours and nobody came. and this time we were able to hem a lot more people, and that was great. >> that was scott pelley reporting. coming up after your local news on "cbs this morning," the

latest on the investigation into the boston marathon bombing. we'll speak with john miller. plus, we will remember those who were killed in that terror attack. and we'll speak with golfer adam scott. reigning masters champion. that's the "cbs morning news" for this wednesday. thanks for watching. i'm anne-marie green. have a great day. masters champion. that's the "cbs morning news" for this wednesday. thanks for watching. i'm anne-marie green. have a great day. -- captions by vitac -- www.vitac.com

>> your realtime captioner: linda marie macdonald good morning, everyone. hey, wednesday is here, it's april 17. i'm frank mallicoat. and michelle has the day off. >> yeah. one more day off. and i'm elizabeth wenger. let's go over and get a check of weather and traffic. here's a look with lawrence. >> a look with lawrence.

a new look. >> feeling good today, guys. hey, you know, we have more sunshine coming our way today. the temperatures are going to heat up more so, fairly mild in spots right now into the 40s and 50s. could break 70s toward the afternoon. we'll talk about that coming up. >> we like that. there's no big hot spots on the road. so we'll check that coming up. we begin with the fbi appealing for anybody information that could help the investigation of that boston marathon bombing. some exclusive photos from fox 5 atlanta show what remains of those boston bombs. the feds say they were made from pressure cookers packed with shrapnel. they will try to determine who built them. tips have been pouring into the fbi. more than 2,000 so far. cbs reporter susan mcginnis