Ian David Long identified as California shooting suspect

The perpetrator of the shooting incident in the Borderline Bar and Grill in California's Thousand Oaks city was on Thursday identified as Ian David Long.

Ventura County Sheriff Geoff Dean confirmed that the 28-year-old was found dead in an office near the bar, CNN reported. "We believe he shot himself," Dean said.

A former US Marine Corps veteran Long used a Glock 21 .45-caliber handgun with an extended magazine for the shooting.

"We have no idea what the motive was at this point," Dean said, adding that deputies were conducting searches at Long's house.

According to investigators, Long drove to the bar on Wednesday night and shot a security guard posted outside before entering, following which, he first shot other security workers and bar employees before open firing into the crowd.

At least 13 people were killed in the incident, including Ventura County Sergeant Ron Helus, who Dean labeled a hero.

Long has had previous encounters with the police. In April, officers were called to his house over a disturbance.

"He was somewhat irate, acting a little irrationally," Dean said about the incident. Mental health evaluations did not deem him eligible to be held under California's 5150 mental health detention law.

Long was also the victim of a battery incident in a bar in the city in 2015.