The inquest -- the first conducted in Los Angeles County in more that 30 years -- found that Guardado's "manner of death was by the hands of another person other than by accident," wrote retired California Court of Appeals Justice Candace D. Cooper, who oversaw the probe. His cause of death was multiple gunshot wounds, she wrote.
The findings were based on testimony from medical experts, investigators and witnesses at the scene when Guardado was shot at by deputies, as well as subpoenaed records from the Los Angeles County Sheriff's Department, which were not released publicly.
Independent autopsy reveals 18-year-old was shot 5 times in back by sheriff's deputies
In a statement, Guardado's parents, Cristobal and Elisa Guardado, said Cooper's finding "has confirmed what we knew all along."
"We now call upon District Attorney (George) Gascon to do what the sheriff's department has not, and that is to take action and hold these deputies accountable for their criminal actions," read the statement, which was sent by the family's attorneys.
"Andres was a good person with his whole life ahead of him. That life was violently taken from him, and we suffer the consequences as his killers remain free. Our family will not rest until we have justice for Andres."
Gascon's office did not immediately respond to a request for comment on the family's remarks made after the close of usual business hours.
During the Nov. 30 inquest proceedings, multiple members of the sheriff's department declined to answer questions, citing advice from attorneys.
Among them were Deputy Christopher Hernandez, who was present during the shooting but did not fire at Guardado, and two homicide detectives who were assigned to the case -- Mike Davis and Joseph Valencia -- who repeatedly declined to answer questions, saying that under advice from counsel they were invoking their rights under the Constitution.
Cooper excused them, but said she would determine if their blanket refusals to answer questions was appropriate and said they may be called back later.
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Cooper noted in the inquest findings that she had sufficient evidence to conclude the probe without calling more witnesses or requesting more evidence, and for that reason, she wouldn't "pursue the Fifth Amendment issues raised during the inquest."
The officer who shot Guardado, Miguel Vega, also did not attend the Nov. 30 proceeding, and later submitted a declaration "indicating that if he were to appear and be questioned at the inquest, he would assert his Fifth
Amendment right not to testify," Cooper wrote in the inquest findings.
She added that she accepted the declaration in place of an in-person testimony "(g)iven the totality of the circumstances, and out of respond for Deputy Vega's rights under the Constitution."
The death of Guardado, who was shot multiple times in the back, prompted multiple protests and calls for disciplinary action and prosecution of the deputies involved.
The sheriff's department did not immediately respond to a request for comment on the inquest findings made after the close of usual business hours.
Two doctors who conducted autopsies on Guardado confirmed during the Nov. 30 proceedings that he was shot five times in the back.
Lianna Darabedyan, a coroner's investigator assigned to the case, testified that a gun was found about three to five feet to the right side of Guardado's head as his body lay face-down on the ground.
County firefighter/paramedic Andrew Clemens, who responded to the shooting scene, said Guardado was pronounced dead within about three minutes after paramedics arrived.
The sheriff's department has said Guardado was reaching for the gun when he was shot June 18 in a driveway on West Redondo Beach Boulevard in an unincorporated area near Gardena while working as what has been described as an informal security guard for a nearby auto body shop.
Deputies said he was not wearing a guard's uniform when they responded to a report of a non-fatal shooting in the area, and that he wasn't licensed as a guard or old enough to hold that job under state law.
Guardado's family has filed a suit against the county alleging wrongful death and civil rights violations.
An inquest into another fatal shooting by a Los Angeles County deputy is scheduled for Jan. 28. Cooper was also appointed by the coroner's office to investigate the death of Fred Williams III, who was shot and killed by deputies Oct. 16 while running away from them with a handgun.