A grand jury has declined to bring charges against an off-duty Los Angeles police officer who shot and killed a man with developmental disabilities in a Costco in June.

Riverside County District Attorney Mike Hestrin announced the decision at a news conference Wednesday.

Hestrin said the results of the investigation were presented to a grand jury this month, and the panel declined to return charges.

Kenneth French, 32, with his parents, Russell and Paola French. Rick Shureih / via Facebook

"One of the pieces of information that I think was uncontroverted was that the off-duty officer was struck by Kenneth French — struck in the head — and he went down as he was holding his infant child," Hestrin said. "And it all happened very fast, about less than four seconds from the moment that he (French) struck to the moment that he (Sanchez) fired."

Salvador Sanchez opened fire June 14 at a Costco in Corona, east of Los Angeles, fatally shooting Kenneth French, 32, and injuring his parents, Russell and Paola French.

Russell French was shot in his chest and abdomen and lost a kidney. Paola French was shot in the back and ended up in a coma.

An attorney for Sanchez, David Winslow, previously said the officer was shopping in Costco with his wife and had his son in his arms when they were "both knocked to the ground." Sanchez said he was assaulted without provocation.

An attorney for the French family has said family members believed Kenneth French, who was nonverbal, suffered from schizophrenia and was off his medication at the time.

Russell French said at a news conference last month that he "begged" Sanchez not to fire. "I told him we had no guns and my son was sick."