THOUSAND OAKS, Calif. — Investigators are looking for evidence Friday morning that shows any kind of motivation for the mass shooting at a California bar that left 12 dead, not including the gunman.

Investigators are combing through the shooter's home and car. The FBI says the shooter was 28-year-old Ian David Long, a former marine.

On his Facebook page investigators found messages saying, "I hope people call me insane ..."

They say he killed 12 people at the Borderline Bar and Grill in Thousand Oaks California before taking his own life.

Long was described by his neighbors as distant in public, but argumentative with his mother inside their suburban Los Angeles' home.

Officials say Long had previous encounters with law enforcement and as recently as April had to meet with mental health specialists.

One ruckus in April was so extreme that they called law enforcement. Authorities brought in a mental health specialist who concluded that Long could not be involuntarily committed for psychiatric observation but worried that Long might have post-traumatic stress disorder.

"The mental health experts out there cleared him that day," Ventura County Sheriff Geoff Dean said Thursday.

Julie Hanson, who lives next door to Long's ranch-style home, described him as “odd” and "disrespectful" well before he left home a decade ago, got married and enlisted in the Marines, becoming a machine gunner.

She could often hear him yelling and cursing, but several months ago, unusually loud banging and shouting prompted her husband to call authorities.

"I was concerned because I knew he had been in the military," Tom Hanson said Thursday, as federal and local law enforcement officers searched Long's house, where an American flag flew over the garage.

Other than the call in April, Long’s only other contact with authorities came after a traffic collision and after he alleged he was the victim of a violent encounter in 2015 at another bar in Thousand Oaks, the sheriff said.

Long joined the Marines at 18 and was married as a 19-year-old in Honolulu in June 2009, according to military and court records.

His military service lasted nearly five years, and he was honorably discharged with the rank of corporal in 2013, the Pentagon said. He was part of the infantry, responsible for hauling and shooting machine guns.

During his service, Long’s marriage fell apart. He and his wife separated in June 2011, while he was deployed on a seven-month tour in Afghanistan. The couple cited irreconcilable differences in divorce papers filed in May 2013, two months after Long left the Marines.

Later, he enrolled at nearby California State University, Northridge, last attending in 2016, the school said in a statement.

More recently, he was living in a home where neighbors said they could hear frequent, aggressive shouting between Long and his mother, especially over the last year.

Among the dead is Sgt. Ron Helus, who worked with the Sheriff's Office for 29 years and was thinking about retirement. He's survived by a wife and son. Dean said Helus was speaking to his wife right before answering the call that would be his last.

Meanwhile, more is being learned about some of the victims.

  • Dan Manrique: a Marine corps vet.
  • Justin Meek: a recent grad of California Lutheran University.
  • And 21 year-old Noel Sparks was reportedly a student at Moorpark College.

The Associated Press contributed to this story.