• Twelve people were killed in a shooting at a bar in Thousand Oaks, California, on Wednesday night.
  • Authorities identified the shooter on Thursday as 28-year-old Ian David Long and said he killed himself after the massacre.
  • Long was a veteran who served from 2008 to 2013, including a stint in Afghanistan between 2010 and 2011, the Marine Corps confirmed.

The gunman who killed 12 people when he opened fire at the Borderline Bar & Grill in the Los Angeles suburb of Thousand Oaks on Wednesday night has been identified as 28-year-old Ian David Long.

Ventura County Sheriff Geoff Dean said at a press conference Thursday morning that authorities believe Long fatally shot himself after the massacre.

Long was a veteran who served in the US military from 2008 to 2013, including a stint in Afghanistan from 2010 to 2011, the Marine Corps confirmed in a statement.

Dean said his deputies had encountered Long prior to Wednesday night, and even visited his home last April and found him acting “irate” and “irrationally.”

Though deputies summoned mental-health specialists to the scene, they declined to take him to a psychiatric facility for involuntary commitment, saying he didn't meet the criteria, Dean said.

Read more: Authorities visited the Thousand Oaks shooter earlier this year, but didn't take him in

Here's what else we know so far, from witnesses and police authorities, about Long:

  • He used a Glock 21 .45-caliber handgun.
  • Authorities said the handgun was purchased legally, but the extended magazine it was outfitted with was illegal.
  • A witness told KABC-TV the gunman reloaded the gun at least once.
  • Witnesses said he used a smoke grenade, but police haven't confirmed that yet.
  • Witnesses said the gunman wore all black, including a black hat, glasses and a black shirt. Dean confirmed Long was wearing a black sweater.
  • Law enforcement sources told the Los Angeles Times that the gunman drove his mother's car to the attack.
  • Authorities said they're still obtaining warrants to search Long's residence and the car he drove to the bar.

This story is developing. Refresh for updates.