Southern California city mourns in wake of bar massacre

One of the safest cities in America is struggling to cope with the trauma of a mass shooting while authorities are trying to figure out what sent a Marine veteran on a bloody rampage in Southern California.

Hundreds of people gathered Thursday night at a vigil to remember the dozen people shot down by 28-year-old Ian Long one night earlier at the packed Borderline Bar & Grill. 

Neighbours of Long have described the man as distant in public but combative with his mother inside the suburban Los Angeles home the two shared.

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 the 28-year-old Marine veteran might have post-traumatic stress disorder.

Next-door neighbour Julie Hanson described him as "odd'' and "disrespectful'' well before he left home a decade ago, got married and enlisted in the Marines.

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

Tom Hanson says he's "dumbfounded'' by the massacre.

Long apparently took his own life as police converged on the Thousand Oaks nightspot.

Terrified patrons hurled barstools through windows to escape or threw their bodies protectively on top of friends as shots erupted.

Ventura County sheriff's Sgt. Ron Helus was shot as he entered the bar.

The dead also included a man who had survived last year's massacre in Las Vegas.