Shock and heartbreak follow California shooting

THOUSAND OAKS, CA (NBC) - Families, friends and the greater community gathered together in mourning Thursday night after 12 people were killed in a mass shooting at a bar in Thousand Oaks, California.

The area was known as one of the safest in the country until Wednesday night's shooting.

Authorities say a Marine veteran opened fire inside the Borderline Bar and Grill, killing a dozen people before turning the gun on himself.

Many of the victims were from local colleges, including Pepperdine University and Moorpark College.

Ventura County Sheriff Sergeant Ron Helus was also killed when he rushed inside the bar to try to stop the shooter.

Investigators are working on a timeline for the shooting, and they have not yet determined a motive.