A third suspect has been charged in connection with the fatal shooting of an off-duty Monterey Park police officer in Downey last week.

Gerardo Magallanes, 18, faces one count of murder, shooting at an occupied vehicle and unlawful possession of a firearm while on probation, according to the Los Angeles County District Attorney’s Office.

Magallanes, of San Pedro, was arrested Aug. 11, three days after Officer Gardiel Solorio was shot to death in the parking lot of an L.A. Fitness.

Carlos Daniel Delcid, 20, and a 17-year-old have already been charged in the killing.

An investigation revealed the teen drove Delcid and Magallanes to the parking lot. Delcid alleged got out of the vehicle he was in, approached Solorio while armed with a gun, tried to rob the off-duty officer and take his car, officials said.

Delcid allegedly shot Solorio multiple times as the victim backed out of a parking space. Delcid then ran back to the waiting vehicle and the three drove away from the area.

Delcid has been charged with one count each of murder, shooting at an occupied vehicle and possession of a firearm by a felon. He also faces a special circumstance allegation that the killing was committed during a carjacking, officials said.

The unidentified minor has been charged with murder in Juvenile Court.

Magallanes is scheduled to be arraigned Sept. 8.

Solorio, 26, was hired as a police recruit earlier this year and had just started field training in late July. He was described as being hardworking, dedicated and family-oriented. The Bell Gardens native is survived by his parents, brothers, sisters and fiancé.