Updated at 4:57 p.m. ET
Authorities have identified the suspect who killed 12 people at a country music bar in Thousand Oaks, Calif., as 28-year-old Ian David Long.
Long, who apparently killed himself, was a Marine Corps veteran and was known to local law enforcement.
Ventura County Sheriff Geoff Dean said during a news conference Thursday morning that his department has had "several contacts with Mr. Long over the years" including minor events such as a traffic collision. Long was also the victim of battery at a local bar in 2015.
In April, there was a troubling incident in which deputies were called to Long's house after reports of a disturbance.
"They went to the house. They talked to him," Dean said. "He was somewhat irate, acting a little irrationally."
Deputies called the crisis intervention team, and mental health specialist who met with Long. The specialist didn't feel that Long qualified to be detained under 5150, the California law that allows for a 72-hour psychiatric evaluation if a person is deemed a danger to himself or others. Long was left at the scene at that time, the sheriff said.
Long served in the Marines from August 2008 until March 2013. A machine gunner who attained the rank of corporal, he served about seven months in Afghanistan, from November 2010 to June 2011. His last duty station was at Kaneohe Bay, Hawaii.
Dean said that when deputies were dispatched to Long's residence in April, there was concern that, given his status as a veteran, he might be suffering from PTSD. The Department of Veterans Affairs said on Thursday that Long was not enrolled in VA health care at any time.
A Pentagon official told NPR's Tom Bowman that Long "was not a stellar Marine." The official says Long received two infractions in 2009 for shoplifting at a post exchange. Long received an administrative punishment, but it wasn't enough to force him from service and he was honorably discharged. Long received no personal awards aside from the Combat Action Ribbon, which is given to anyone who is fired on by the enemy or fires at the enemy.
Court records show Long was married in 2009, separated in 2011 and divorced in 2013, The Associated Press reports. The president of California State University, Northridge, said in a statement that Long was a former student at the school, most recently in 2016.
Long lived with his mother at a house she owns in the nearby town of Newbury Park. On Thursday morning, deputies were outside the house as they sought a warrant to conduct a thorough search of the property.
A neighbor, Tom Hanson, told local television station KTLA that he and other neighbors knew Long "had issues." He described an incident — which seems to match the April episode mentioned by the sheriff — in which he called law enforcement to Long's house because it "sounded like he was tearing down the walls of the house, like somebody's just beating on the walls with a big hammer or something."
Since that incident, Hanson said, things had quieted down. He said he had assumed Long must be getting treatment of some kind.
When Long approached the Borderline Bar & Grill in Thousand Oaks, he used a Glock 21 .45 caliber handgun that he purchased legally, according to Dean. The weapon had an extended magazine, but law enforcement has not determined how many rounds it could hold with the modification, or whether the shooter reloaded the weapon during the shooting.
Law enforcement has not confirmed witness reports that Long set off smoke bombs at the bar.
Authorities were still working to identify the victims and inform their families.
NPR National Desk editor and producer Evie Stone contributed to this report.