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The California sheriff tasked with pursuing charges against the four alleged gang members accused in the shooting death of an off-duty Los Angeles Police Department officer says he took the case to federal prosecutors because the response from the local district attorney’s office was "not satisfactory" and "really did not cover the depravity of this crime." 

Los Angeles County Sheriff Alex Villanueva made the comments to the Los Angeles Times.

Luis Alfredo De La Rosa Rios, 29; Ernesto Cisneros, 22; Jesse Contreras, 34; and Rios’ girlfriend Haylee Marie Grisham, 18, are expected to appear in court Friday after being charged in the killing of off-duty officer Fernando Arroyos. The 27-year-old was gunned down Monday in South Los Angeles during an attempted robbery while he was looking at houses with his girlfriend, authorities said. 

"I believe their plan was to just prosecute a simple murder with no gun enhancements, no gang enhancements, nothing," Villanueva told the Los Angeles Times when asked if he had consulted with Los Angeles County District Attorney George Gascon’s office. "And that really did not cover the depravity of this crime…. It should be noted that the California penal code does cover all these things. The tools are there but we need to have someone who’s willing to use them." 

Los Angeles police officer Fernando Arroyos, 27, was killed Monday night while house hunting with his girlfriend. Four people have been arrested in connection with the murder investigation, the Los Angeles County Sheriff's Department said Wednesday.

Los Angeles police officer Fernando Arroyos, 27, was killed Monday night while house hunting with his girlfriend. Four people have been arrested in connection with the murder investigation, the Los Angeles County Sheriff's Department said Wednesday. (Los Angeles Police Protective League)

JUSTICE DEPARTMENT CHARGES 4 SUSPECTS IN LAPD OFFICER’S DEATH 

The U.S. Attorney’s Office for the Central District of California ultimately charged the four suspects with violent crime in aid of racketeering, which it says "carries a potential death penalty – and minimum sentence of life in federal prison without the possibility of parole – because Officer Arroyos allegedly was murdered during the robbery." 

Sources also said Villanueva went to federal authorities to handle the situation because of Gascon’s decision to no longer pursue sentencing enhancements in gang-related cases. The DA's decision on enhancements affects whether criminals are given a chance at parole, the Los Angeles Times reported. 

Villanueva also told the newspaper that the DA's response was "not satisfactory." 

When asked to respond to Villanueva's comments, Alex Bastian, Special Advisor to District Attorney George Gascon, told Fox News Digital that "we support the federal authorities taking the case and will be in communication with all the parties involved."

"It was indicated to us that the case was referred to the federal authorities, who filed charges," he added. "As such, we did not have an opportunity to review the case."

L.A. Police Chief Michel Moore reportedly said Thursday following the arrests that he was "grateful for the federal involvement in this case.

"It is appropriate. I am thankful for the U.S. attorney stepping in and bringing the full weight of the government against this gang, against these individuals," the Los Angeles Times quoted him as saying.

Police investigate after an off-duty LAPD officer was killed in a shooting in South Los Angeles.

Police investigate after an off-duty LAPD officer was killed in a shooting in South Los Angeles. (FOX 11 Los Angeles (KTTV))

The suspects drove up to the house Arroyos and his girlfriend were looking at Monday night and Rios and Cisneros robbed them at gunpoint, according to a statement from the Justice Department. 

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Arroyos reportedly exchanged gunfire with one of the suspects and was hit once. He collapsed in an alley and later died at a hospital.  

The suspects allegedly fled after Arroyos was hit.  

Investigators have surveillance video of the suspects going to another home after the shooting, according to the release, which also alleges they carried out the attack "to increase and maintain position" within the Florencia 13 gang. 

"F13 is a large, multi-generational street gang that previously has been the subject of federal prosecutions, including two large racketeering cases," it added. 

In an interview with Fox News in December, Villanueva accused Gascon of being "careless and irresponsible," claiming the work of law enforcement officers in the state was being undermined by liberal policies and reforms put in place by some district attorneys. 

The sheriff said in Los Angeles County there have been more than 12,000 cases in which Gascon has declined to prosecute suspects apprehended by county deputies after alleged crimes. 

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"So that is disheartening for any cop to think all their work is being undone by a careless and irresponsible district attorney. But they’re not going to stop doing their job," Villanueva said.  

"So we’re making the effort out there," he added. "What we need now is, we need responsible district attorneys who are going to file their cases. And if they want to play the role of public defender, they should just quit their job and go over to the public defenders – and everything they say makes perfect sense for a public defender, not a district attorney." 

Fox News’ Brie Stimson contributed to this report.