LOS ANGELES (CNS) — Three suspected members and an associate of a street gang are expected to make their initial federal court appearances Friday in downtown Los Angeles in connection with the fatal shooting of a 27-year-old off-duty Los Angeles Police Department officer.

The three men and the 18-year-old girlfriend of one of them were charged late Thursday with violating a federal racketeering statute for their roles in the robbery and fatal shooting of Officer Fernando Arroyos on Monday night, according to U.S. Attorney Tracy L. Wilkison.

The charge of violent crime in aid of racketeering carries a potential death penalty and a minimum sentence of life in federal prison without the possibility of parole because the fatal shooting occurred during a robbery, Wilkison said.

The defendants are expected to make their initial appearances in U.S. District Court after 1 p.m.

Charged with violent crime in aid of racketeering to increase and maintain position within the Florencia 13 gang were:

—  Luis Alfredo De La Rosa Rios, 29, an F13 member also known as "Lil J";

—  Ernesto Cisneros, 22, an F13 member also known as "Gonzo";

—  Jesse Contreras, 34, an F13 member who claimed a moniker of "Skinny Jack," but who also may be known as "Flaco"; and

—  Haylee Marie Grisham, 18, Rios' girlfriend.

Los Angeles County Sheriff Alex Villanueva said he directed detectives to take the case to the U.S. Attorney's Office because of his opposition to District Attorney George Gascon's decision to no longer pursue sentencing enhancements in gang cases.

Those enhancements in a murder case can mean the difference between a life term with the possibility of parole and never being released from prison.

Villanueva told reporters at a Thursday night news conference that a murder prosecution "with no gun enhancements, no gang enhancements, nothing ... 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."

LAPD Chief Michel Moore said 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 shooting occurred about 9:15 p.m. Monday in the 8700 block of Beach Street, near Firestone Boulevard, in the unincorporated Firestone- Florence area, authorities said.

According to a sworn affidavit from an FBI agent, Rios admitted in an interview with sheriff's detectives his involvement in the killing, saying he and the other defendants were driving around looking to "make money," which he further explained meant to rob a person of property or money.

The complaint alleges that Rios and Cisneros exited a black pickup and confronted Arroyos, a three-year veteran of the LAPD, and his girlfriend as they were searching for a home to purchase in the area.

The two allegedly pointed guns at the victims and removed property from both, including a wallet and two silver chains from Arroyos' neck, said sheriff's Capt. Joe Mendoza

"At some point after Cisneros removed (Arroyos') chains, (Arroyos) and the two suspects exchanged gunfire," according to the complaint.

Arroyos sustained a single gunshot wound, ran from the area and collapsed in an alley as the two suspects fled the scene in the truck.

Responding sheriff's deputies arrived at the scene and found bystanders performing CPR on Arroyos, Mendoza said. The deputies loaded Arroyos into a patrol car and took him to a hospital, where he was pronounced dead.

Detectives retrieved a loaded handgun from the scene belonging to one of the suspects, and the sheriff's department received a report about 9:25 p.m. Monday of a man suffering a gunshot wound in the area of Junction Street and East 60th Street about a mile-and-a-half from the site of the shooting, Mendoza said.

Investigators later determined the wounded man was Cisneros and he was shot during the exchange with Arroyos. Contreras was also found in the area hiding inside the garage of his residence in the 5900 block of Junction Street.

A second handgun was retrieved from Contreras' residence and will be tested to determine if it was used in the shooting, Mendoza said.

Rios and Graham were later found and taken into custody at their residence.