A gunman has opened fire at a country music bar during a student night in the city of Thousand Oaks, California, killing 12 people and injuring several before turning the gun on himself.
The shooter stormed the Borderline Bar and Grill wearing a black trenchcoat armed with a pistol equipped with an extended magazine and smoke grenades began targeting people as young as 18.
Ron Helus - a Ventura County sheriff sergeant - was among the deceased. The 'hardworking' officer, who was due to retire this year, had 29 years of experience in the force and leaves behind a wife and son.
An additional '10 to 15' victims were injured during the mass shooting, including a doorman, a young female cashier and college students.
The perpetrator, dressed in all-black, wearing a baseball cap, sunglasses and a mask covering the bottom part of his face, walked up to the entrance at 11.20pm and shot the doorman before making his way into the venue.
He then opened fire on a young female cashier before throwing smoke grenades onto the dancefloor and letting off rounds into the crowd.
First responders from the Ventura County Sheriff's Office and Highway Patrol arrived at 11.23pm and got into a gunfight with the suspect, during which a deputy sheriff was shot and later died at Los Robles Hospital from his injuries.
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