Updated

The parents of a 13-year-old boy say they felt they had lost their son again after prosecutors said they would not file criminal charges against a Northern California sheriff's deputy who shot and killed him, mistaking a pellet gun he was carrying for an assault rifle.

The parents of Andy Lopez decried the decision announced Monday by the Sonoma County District Attorney Jill Ravitch, calling it "impossible" to accept.

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

After the announcement, about 100 protesters marched through the streets of Santa Rosa, where Lopez's death aggravated racial tensions in his mostly Latino neighborhood in the city of about 170,000 people north of San Francisco.

The protesters focused on both the deputy, Erick Gelhaus, and the district attorney they say gave him a pass.

"She's giving permission to the deputies to kill our children and kill us -- people in the community -- and get a paid vacation and no repercussions," Nicole Guerra, whose son was a close friend of Lopez's, told the Santa Rosa Press Democrat.

Gelhaus fired multiple rounds in response to what he believed was an imminent threat of death, Ravitch said 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. 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.

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.

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."