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Ian Long, 28, opened fire at Borderline Bar and Grill in Thousand Oaks at 11.20pm on Wednesday night
He was dressed in all-black and used a legally owned .45 caliber handgun which had an extended magazine
Witnesses said he also let off smoke grenades inside to confuse the terrified crowds as they ran for their lives
In April, police and mental health specialists were called to Long's home after neighbors heard crashes coming from inside
They decided he was not qualified to be committed involuntarily and left him at home with his mother
Neighbors told DailyMail.com on Thursday that she lived 'in fear' he was going to harm himself
Long served in the Marines for five years between 2008 and 2013 during which time he was given 10 medals and toured Afghanistan
After leaving the Marines, he spent three years studying athletic training at California State University Northridge but he dropped out in 2016
A college roommate of his said he was 'mean', a 'loner' and would often dance in their garage alone
He killed himself on Wednesday in an office in the bar after killing 11 patrons and a sheriff's sergeant who responded