functioning like an automatic machine gun. the gunman firing bullets continuously. listen. the unmistakable sound different from anything we've heard from all other recent mass shootings. none of them involving fully automatic guns. >> we are still going through the search warrant actively at this time, but it's in access of ten rifles. >> reporter: sources telling abc news paddock had at least 16 rifles and handguns. one of them an assault rifle, modified to fire like a machine gun. sources say some of the rifles were high powered, capable of slicing through police body armor. >> this is a classic wmd, this is a weapon and a man of mass destruction. >> reporter: we examined the first 90 seconds of the massacre, hearing nearly 200 rounds fired. hundreds more within the following minutes. paddock took brief pauses, likely to switch weapons or reload. the killer perched more than 300