The investigation looked into many different factors such as the fact that Derrick Gaines, 15, had drugs on him and in his system when he died, but mostly, it came down to his possession of a gun.
"I have concluded that the officer's conduct under the circumstances was reasonable and justifiable within the guidelines of the California penal code," said San Mateo County District Attorney Steve Wagstaffe.
Wagstaffe made the determination after reviewing the evidence. The night of June 5th, Gaines and a friend were walking through the Arco station at the corner of Wesborough and Gellert in South San Francisco. Police Officer Joshua Cabillo approached the two because they were acting suspiciously. You can see Gaines take off in a surveillance video. When Cabillo caught up with him, there was a confrontation. The district attorney says Gaines had a gun and reached for it.
"Clearly the most significant factor was the existence of this .45 caliber firearm that the young man had in his possession and was reaching for at the time the officer made the decision to fire and kill him," said Wagstaffe.
What Cabillo didn't know was that the gun was inoperable.
"I've seen the gun and it was not apparent by looking at it that it was missing the firing pin and was inoperable," said Wagstaffe. However, Gaines did know. "He very much knew that that gun was not an operable gun."
ABC7 spoke to the boy's stepfather on Wednesday and he says the family is disappointed with the district attorney's finding, but isn't surprised. Their civil rights lawyer, John Burris, has filed a civil suit.
"This young man and another young man were just walking along and they were just stopped by police with no apparent reason, without an actual basis?kind of a classic racial profiling," said Burris.
Burris says he has witnesses who will say that Gaines didn't reach for anything, but of course the district attorney's office also has their witnesses that say that he did.
The family will be holding a rally for Gaines the Arco station on what would be his 16th birthday coming up on Sept. 20.