SANTA ROSA, Calif. (AP) — Prosecutors said Monday they will not file criminal charges against a Northern California sheriff’s deputy who shot and killed a 13-year-old boy carrying a pellet gun he mistook for an assault rifle.

The parents of Andy Lopez decried the decision, saying “it is impossible” to accept and they felt as though their son “had been killed again.”

The teen’s death last year heightened racial tensions in a mostly Latino neighborhood of Santa Rosa, a city of about 170,000 residents around 50 miles north of San Francisco. The shooting parked protests and criticism that the officer acted too quickly.

Deputy Erick Gelhaus fired multiple rounds in response to what he believed was an imminent threat of death, Sonoma County District Attorney Jill Ravitch announced at a news conference.

“While in the lawful performance of his duty, Deputy Gelhaus was faced with a highly unpredictable and rapidly evolving situation,” Ravitch said. “He believed honestly and reasonably that he was faced with a do-or-die dilemma.”

Ravitch displayed photographs of the pellet gun found next to Lopez and a real assault rifle to highlight similarities in appearance.

Gelhaus shot Lopez on Oct. 22 as the teen walked near his home with the pellet gun. The deputy told investigators he believed the gun was real and opened fire out of fear for his life.

At least one witness said he heard the deputy order Lopez to drop the pellet gun before shooting, Ravitch said.

Gelhaus fired eight times, striking the eighth-grader seven times with his department-issued 9 mm handgun. The district attorney said Gelhaus had 18 rounds in his gun and stopped shooting when he felt the threat had ended. Lopez was declared dead at the scene.

“This disheartening decision leaves the family feeling as though Andy had been killed again today,” Lopez parents said in a prepared statement released by their lawyer, Arnoldo Casillas.

Casillas represents the family in a wrongful death lawsuit filed in federal court in San Francisco against the county and Gelhaus, which has been on hold pending the outcome of the district attorney’s investigation. Casillas said he will petition the court to restart the litigation.

Casillas said “it is impossible” to accept Ravitch’s conclusions and that he and the family are asking federal officials to investigate.

The FBI said it is looking into the shooting to determine if any civil rights violations occurred. The district attorney forwarded her report to federal investigators.

FBI agent Brian Weber said investigators have “collected and reviewed documents and other evidence produced in connection with this matter and is working with the United States Attorney’s Office and the Department of Justice in Washington, D.C.” Weber declined further comment.

Those who have protested the shooting said the deputy did not give ample warning before opening fire. Investigators have said 10 seconds elapsed between the time Gelhaus and a trainee reported a “suspicious person” and then reported shots fired to dispatchers. The trainee did not open fire.

Ravitch said her office’s findings will not alleviate the pain felt by Lopez’s family or the community.

“This is a painful, painful chapter in the history of Sonoma County,” Ravitch said. “While it was absolutely a tragedy, it was not a criminal act.”

Sonoma County Sheriff Steve Freitas said an internal investigation also concluded Gelhaus and his partner acted appropriately and that the department would now evaluate the incident to determine if “there are things we can do differently going forward, or to improve performance in general.”

Freitas called for passage of a state Senate bill introduced in January that would require pellet guns to look clearly different from those that fire bullets.

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