Investigators are looking into the mental state of the accused Fort Hood shooter. Some say he may have been struggling with the recent deaths of his mother and grandmother.
34-year-old Ivan Lopez served four months in Iraq as a truck driver but didn't see any combat. Upon his return home, he reported a traumatic brain injury...and sought treatment for anxiety and depression, but officials say it may have been an argument at Fort Hood that set him off:
"There may have been a verbal altercation with another solider or soldiers and there is a strong possibility that may have immediately proceeded the shooting," said Lt. Gen. Mark Milley.
Authorities say Lopez fired shots in two buildings on post and from a vehicle using a 45-caliber semi-automatic pistol he recently purchased.
"Obviously it had to be somewhat planned," said CBS News Military Analyst Maj. Mike Lyons (Ret.). "He purchased a handgun off the base. Somebody along the way must have gotten the hint."
Investigators are questioning Lopez's family including his wife, and are going through his computer files for clues about a possible motive.
At least three people were killed in the shooting Wednesday, including 37-year-old Army Sergeant Tim Owens from Illinois.
"It's really hard to take I'm stunned, I really am, that this could happen," said Paul Eatherton.
Owens' mother told CBS News her son was trying to calm Lopez down when he was shot multiple time.
More than a dozen others were wounded. Officials say there was no indication Lopez was targeting specific people.
Fort Hood was the site of the deadliest shooting on a U.S. military installation in 2009 when Army psychiatrist Nidal Hasan killed 13 people and wounded 30.