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ANTIOCH, Calif. - Antioch gas station clerk James Williams chased after an armed robbery suspect and shot him and then kept on firing, authorities said.
The suspect then shot the clerk in the chest and leg, killing him.
Contra Costa County prosecutors announced they won't be charging the suspect with murder.
"What was most problematic was in this case that Mr. Williams engaged these individuals from behind with a firearm," said Derek Butts, a deputy district attorney.
At a news conference Friday, prosecutors described why, under state law, the store clerk went over the line when he opened fire on two robbers who were running away.
The shootout happened at the Chevron Extra Mile store on Contra Loma Boulevard near Highway 4 at about 2 a.m. Saturday.
Two men went into the store. Authorities say one of them, Ronald Jackson III, 20, brandished a gun, and they stole about $200 from the register and tobacco products before running out of the store.
But the clerk then chased after the robbers and opened fire, hitting Jackson in the leg. The suspect fell to the ground.
"And after hitting one, continued to fire," Butts said. "This was very dynamic, but a total of nine shots were fired by Mr. Williams."
Some of those shots hit a home across the street from the gas station. A second robber escaped.
Authorities say the tables were turned - the store clerk became the aggressor, and the robbers became the victims.
"Now they are under a deadly attack, when such attack was not legally justified," Butts said.
"While the two perpetrators of that robbery are by no means noble individuals…their life is valued, under the law, greater than any claim of property," said Simon O'Connell, chief assistant district attorney.
Ken Raider, a friend of the clerk, said Williams likely felt he was in the right.
"I like James and I don't think he's a bad guy, I don't think he's trigger-happy," Raider said
Raider said he wished the suspect was charged with murder but understands the DA's hands are tied.
"They were leaving. OK? He should have just let them go. It wasn't worth it for the cigars, whatever they got," Raider said.