>> jimmy: reggie watts! reggie watts, check out his youtube channel to see more of his work, including "the social music experiment." i want to thank mark ruffalo, raymond gao and kevin bowerman. apologies to matt damon, we ran out of time. thanks for watching. "nightline" is next. good night. tonight on "nightline." moment of crisis. two suspected terrorists taken down by london police. minutes after committing a brutal and very public murder. we ree've got the chilling vide. also tonight, new details coming out about these men, their victims and the one witness who became a hero. just in time for the holiday weekend, meet the buddies who say they could save you hundreds

of dollars a year. all through smart use of your smart phone. but does their system really work? and secret cinema. tonight, the movie craze that makes you the star.

. good evening. as we come on the air tonight, we're getting our first look at the moment when police in london arrived to confront the two terror suspects who had allegedly just murdered a young soldier in cold blood and in broad daylight. this is an i a tack that has genuinely shocked the world. today we learned a lot more about the suspects, their victim and a brave woman who just happened to be there on the scene. we're going to start tonight, though, with that new video.

we warn you, it is graphic. >> reporter: two attackers, taken down by police in london after a nightmare attack in broad daylight. an offduty british soldier, viciously hit by a car and then hacked to death by men armed with meat cleavers and knives, shouting god is great. moments later, one of them, his hands covered in blood invited bystanders to film him. >> you people will never be safe. your government don't care about you. >> one of the attackers has been identified as 28-year-old michael adebelojo. the body of 25-year-old afghan war vet and father of a 2-year-old was left in the middle of the street after he was brutally stabbed. one of the attackers even asked people to call police, luring them into a shootout.

the final moments captured on a kroel f cell phone as this rang out. this shows police gunning down the two suspects in the streets. but some citizens ran towards the scene, trying to aid the dying soldier. >> he's standing there with the knife before the police come for about 20 minutes. people were literally going up to the guy and he was standing there with a knife. >> reporter: amidst, the horror, heroes emerge. this woman rushed to give first aid in vain and finally confronted the attacker. >> i saw a butcher's knife and blood all over him. >> were you not scared for yourself in that situation? >> no. >> why not? >> better me than a child. i talked to him and then i asked

him what he wanted. >> reporter: she earned the praise of prime minister david cameron. >> when told by the attacker he wanted to start a war in london, she relied you're going to lose. it is only you versus many. she spoke for us all. >> reporter: it is the brutality and unsophisticated nature of the attack that sets this apart and has left many questions. >> reporter: it's almost impossible to know when these attacks are going to occur and it's almost impossible to stop them. you can not intercept orders going to the attackers because the attackers themselves decide when and how to attack. you can't stop them from getting the weapons. because the weapons can be obtained in any store. >> and the killers appear to fit an all-toor familiar pattern. home grown radical men almost impossible to detect.

>> radicalized people living in the country, citizens perhaps of the country. who suddenly shift from being radical to being violent. >> reporter: the attacker can be heard speaking in a south london accent. partly apologizing. he even refers to british soldiers as, quote, our troops. >> tell them to bring our troops back so we can all live in peace. >> reporter: crucially something was missed. he even can be seen here demonstrating in 2007. >> he was a very calm and collective, unassuming, not violent. >> reporter: but he was reportedly arrested in a violent demonstration in 2006 outside london's high court. >> he was someone studying his own religion, a family man. i fought he found some work

somewhere else. and the next thing we know, we heard about him on the news. >> unsophisticated lone attackers in london like the two alleged terrorist brothers who set up bombs in the boston marathon, killing three and virtually shutting down a major american city for days, the type of challenge law enforcement is increasingly faced with. >> they don't have to build sophisticated bombs or have a lot of dry runs for the attack. when they don't tell anybody that they're going to do it, it's virtually impossible for police or for intelligence authorities to know about it or stop it. >> reporter: tonight in london, there have been two additional arrests following a series of police raids at several locations around the country. one close to the murder scene. and additional 1,200 police have been drafted on to london's streets. the attackers are reportedly in separate hospitals under armed guard. police will want to determine if this brutal attack was part of a

wider plot, or whether this was a localized act of terror. lee rigby's family pay tribute to their fallen son saying he would do anything for anyone. all he wanted to do since he was a little boy was be in the army. >> as we said, a father of a 2-year-old child. up here next, we're going to switch gears. our reporter hitting the road with an evangelist for cheap gas. could this guy's profession really save you some serious cash? [ engine revving ]

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cabot...that's pro. >> some people are obsessed with sports. some people memorize music trivia, tonight everyone needs a hobby. tonight you'll meet one man who's very, very passionate about local gas prices. and this man's fixation could actually save you some real money. >> reporter: it's an addiction for many across the country. earning points for entering gas prices. >> okay. >> reporter: you might call abe azar a gas price evangelist. the cheapest i've seen is $3.63 is a gallon. >> so here we are at $3.69. wow. i'm seeing it spike already to $3.76 now. >> reporter: finding cheap gas is his passion.

>> people might say why do it? for me, i do it to save other people money. >> so you're saving everybody in the family quite a bit of money. >> that and at work. >> he does it using a smart phone app called gas buddy. kathy nestor told us about it la year. >> is this almost a borderline addiction? every time you go by a gas station, do you feel compelled to have to put the prices into your app? >> yeah, i guess you could -- if you're going to define addiction like that, yeah. it's an addiction. it's a good thing to be addicted to. >> $4.19. i'm going to update that. >> i have not missed a day in eight years. >> reporter: he says the savings does add up. $500 or $600 a year. >> jimm . >> i need to get some gas. can you check where we can get it. the cheapest price is sunoco on broadw broadway. >> leslie starr, wife and mother of two.

>> it's an easy app. i click on the phone, put in the zip code and shows me eight, ten places on my front screen and i can choose where i need to go. >> reporter: with the price of gas climbing more than 30 cents a gallon in some places, trying to outsmart the rise at the pump. >> we have to plan our day, make sure we hit all the stores in the same area just so that we're not driving all over the town and wasting gas. >> reporter: abe, our eadvantage gist le gbegins the day checkin gas prices and passing the information on to his flock -- his kids. >> are you already at work? >> just to let you know, the prices are up. if you need to get gas, i recommend you get it today. >> reporter: we decided to tag along with leslie and abe to see what tips these gas gurus could pass on. number one, timing matters. >> so where somebody saw it two hours ago, it may not be the price by the time you get there. >> reporter: and what credit

card your gas is charged on can be the difference between extra savings or an extra drain. >> a lot of stations actually will charge a sur charge unless you use their particular gas card. >> i didn't realize that. so if you're paying on the credit card, you can sometimes get an extra fee? >> yes. so i use a nongasoline company card anticipate i get a 5% rebate. >> reporter: another tip -- stay local. just because gas is cheaper somewhere, don't drive out of your way for it. >> does it ever annoy you to see signs of cheaper gas and you just filled up? >> if there's no upcharge, yeah, i would be p.o.'d. if i was 15 cents a gallon less i've driven out of my just so i could feel like i dependeidn't o much for gas. >> check your area groceries. >> we have a store, if you buy certain product, they give you a discount per gallon. >> reporter: how can an app like

gas buddy really help you save money. can it? >> endeed. it's remarkable. a lot of people don't realize how much of a gas exists just in their local markets. and many metro markets will have gas anywhere from 60, 70, 80 cents a gallon. >> so how can you tell when gas prices are about to start rising? one place in town, if that price goes up, you know your gas is going up? >> pretty much any truck stop. they sell a whole lot more gas than other folks. >> reporter: and as gas prices are expected to rise, these gas buddies believe they're the best weapon a consumer can carry. >> this particular bp, their prices are actually higher than the last bp that we passed. >> why is that? >> because they can. >> and up next, inside the developments that wannabe movie stars have been waiting for their entire lives.

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traditionally, those of us who are self-egotistical enough to want to be a movie star but too self-aware to realize we can't do more than simply yell also the screen. but we found something exciting. >> reporter: we all have our favorite movie. mine is "shawshank redemption."

instead of watching your favorite film for the 100th time, imagine being inside it. >> move out of the way. dead man walking. >> welcome to secret cinema. an entertainment experience where the audience becomes the actors. i was sentenced to a crime i didn't commit. >> murder, life. in prison, i was welcomed by the same committee, and the same lack of clothing. and life in prison, well, wasn't very nice. >> i just want people to switch into it to the point they come into secret cinema >> but here's the trick. when i bought my ticket, i didn't know what movie i would be in. and here in london, it's a phenomenon. >> if we could get people to buy a ticket without knowing what

they're going to see, we've uncovered, i think, which the audience has been looking for for some time. there's been more than 20 secret cinemas. prometheus made more money than any british theatre made. on my night in shawshank, this was home. this was dinner, and they put me to work in a candle-making factory. >> you want me to lick your shoe clean? >> that's what i said. >> one of the pastimes, other than drinking beer, is guessing which film it is. because amazinglamazingly, the has stayed. >> what's that? "to kill a mocking bird." that's a good guess. our experience is designed to follow the same arc of the film. >> they shot tommy in the courtyard. >> get down!

>> an immersive experience. >> you get in touch with your criminal nature. >>. >> reporter: and after all of that, we got to watch my favorite movie. >> i love this movie. i always cry at the end. it might be embarrassing. >> oh, no. >> reporter: but i wasn't too embarrassed to play along. and now i can't wait for my next part. >> i don't know. maybe it's just me, i would rather just sit in a chair, relax and eat popcorn. maybe it's just me. it's time for tonight's "closing argument" involving the boy scouts america and the controversial ban on gay scouts. today, the organization announced it's lifting that ban meaning openly gay members will be allowed to join the boy scouts for the first time. tweet us at nightline or at danbharris. "world news now" is coming up soon with overnight breaking

news. tune in tomorrow for the latest on the jodi arias trial. storm systems continuing to batter this country. and we as always are always online at abc news.com. good night, and we'll see you back here tomorrow.