The Kern County sheriff has asked the
Silva, 33, a father of four, was pronounced dead May 8. Witnesses reported seeing several deputies repeatedly strike the man in the head with batons as he lay on the pavement.
Sheriff Donny Youngblood also announced Tuesday that he asked the FBI to analyze two cellphones taken from witnesses who say they recorded the incident.
"I took the unprecedented step of asking the FBI to conduct a parallel investigation," Youngblood told The Times. "Our credibility is at stake here."
Youngblood said he has also placed the officers on paid administrative leave, a decision made in the last 48 hours, based on information they had received. He said he wanted to ensure the safety of the officers on the street.
The cellphones were controversially taken after the witnesses were detained at a home. A search warrant was obtained to access the phones.
The phones were turned over to Bakersfield police for analysis, Youngblood said.
"The analysis by the Bakersfield Police Department confirmed the existence of video footage related to this incident on one phone and no video footage on the second phone. This prompted the subsequent request for further analysis by the FBI," the sheriff's office said in a statement.
On Tuesday, Sheriff's Office personnel transported the phones to the FBI's Sacramento office for analysis, officials said.
Deputies had responded to a report of an intoxicated man. In addition to the deputies and sergeant, two California Highway Patrol officers were involved in the incident.
The department has identified those involved as Deputies Ryan Greer, Tanner Miller, Jeffrey Kelly, Luis Almanza, Brian Brock, David Stephens and Sgt. Douglas Sword.
Youngblood said a cause of death for Silva rests on toxicological tests, which could take 90 to 120 days.
Youngblood cautioned in an interview Monday that it is too early in the investigation to reach any conclusions about Silva's death.
Witnesses described a violent scene in which s deputies repeatedly struck Silva in the head with batons.
"I saw two sheriff's deputies on top of this guy, just beating him," witness Ruben Ceballos said in an interview Monday. "He was screaming in pain ... asking for help. He was incapable of fighting back — he was outnumbered, on the ground. They just beat him up."
One woman frantically called 911, telling the operator: "The guy was laying on the floor and eight sheriffs ran up and started beating him up with sticks. The man is dead laying right here, right now. I got it all on video camera and I'm sending it to the news. These cops have no reason to do this to this man."
The decision to take the witnesses' cellphones has raised further questions about the Kern County sheriff's handling of the incident.
"It makes it look like a coverup," said David Cohn, a lawyer for Silva's children and parents, adding that he has not been able to see the footage. "What we're all concerned about is, 'Are these videos going to be altered? Are they going to be deleted?' "
Youngblood defended the decision to take custody of the phones as a way of preserving possible evidence. The sheriff said his office obtained a search warrant for the phones.