Last Updated Dec 3, 2015 10:23 AM EST
All four guns used by the suspects in the deadly San Bernardino shooting have been traced and they were all purchased legally, the Bureau of Alcohol, Tobacco, Firearms and Explosives confirmed Thursday.
CBS News' Paula Reid reported that two of the guns were purchased by someone who is already known by investigators.
A law enforcement source told CBS News senior investigative producer Pat Milton the weapons were purchased legally in California. The long guns were legally transferred from a friend.
Meredith Davis of the ATF said all four guns were bought four years ago. Davis said California requires paperwork when guns change hands privately but many other states don't.
She also said the rifles involved were .223-caliber - powerful enough to pierce the standard protective vest worn by police officers, and some types of ammo can even plow through walls.
The ATF told CBS News that the traces of the guns were completed within a couple of hours of the request being submitted.
Late Wednesday night, San Bernardino Police Chief Jarrod Burguan identified the suspects as Syed Rizwan Farook, 28, and Tashfeen Malik, 27. They were believed to be the only shooters and both were killed during a shootout with police.
Burguan says the suspects were wearing "assault-style clothing" and were both armed with assault rifles and handguns.
The suspects' clothing was "loaded with magazines for a gunfight," Davis said.
Davis said the suspects also threw a thick-gauge copper pipe out of the SUV, but no explosives were found inside.
The fake pipe bomb was equipped with a piece of material made to look like a wick.