dr. errol sujers, the managing director for tall global corporationnd a a professosoof homeland security at the university of southern california. thanks for joining us, dr. suthers. i want to ask you, investigators are exploring all options in terms of a motive but they are not ruling out terrorism. based on what we know so far and your background, what do you think motivated this shooting? understanding that the target or the victims were at a party for county rkers, that it seemed quite personal. the shooters went to a location that didn't appear to be random. they had specific target knowledge, they understood how to get in and out. the speed of what they were able to accomplish in such an ultra violent way suggests they had personal knowledge of thisis locationon last they appeared to be suicidedid not appear to be suicidal so they had tught about this attack and thought about their escape. >> reporter: surely when you embark on an attack like this, you're not planning on getting away. do

dr. errol suthers, thank you so much. >>> the attack in san bernardino is the latest mass shooting in this country. attacks that have become all too familiar. it's the third deadliest mass shooting in u.s. history. there have been more than 350 mass shootings, four or more people this year. that's an average of more than one per day. there are calls by some this morning to strengthen gun laws in hopes of preventing future mass shootings. one of the loudest kams from the new york "daily news" today. the paper has been critical of lawmakers who have balked at stricter gun laws. as nancy cordes reports, it appears that capitol hill is accession. >> reporter: california democrat biggest opponents of gun laws. >> it's heart breaking to see another mass shooting in this country. looks like a war zone and it's not enough to keep lamenting these things. we have to take action. >> reporter: mass shootings have become so pervasive that hillary clinton was actually talking about guns in orlando minutes be

errol barnett in for victor blackwiell. >> let's begin with this unrelenting severe weather. it's been pounding the south. this region that was hit by a tornado outbreak earlier this week is getting dremp inting dr-digit rain totals. horrible flooding in some spots. today 14 million of us are facing new severe weather threats, and more than 22 million will face it tomorrow. overnight, the death toll from this week's tornado disaster went up, by the way, at least 15 people are now confirmed dead. dozens more are injured across mississippi, arkansas and tennessee. and cnn's nick valencia is following the latest weather system and really the damage it's already done, right, nick? >> it has just been devastating. you mentioned the southern portion of the united states, tennessee, georgia, alabama, mississippi, all of those affected waking up christmas morning had this deal with this terrible weather. this type of damage you're seeing is more typical for springtime. but right now at least 15 people have lost their lives. and that death toll could rise. >> reporter: severe weather batters several southern states. heavy rains hammer parts of alabama. at least 20 inches fell in less than 24 hours at the