Authorities think the shooting was a case of domestic violence that ended with an explosion of gunfire.
Neighbors said it all started off as a Tuesday night backyard barbeque on Trailway Drive with a woman and a man who was her ex-boyfriend.
Riverside Police identified the woman as Arabella Bradford, 38. Marvin Conley, 43, was also fatally shot. Virgil Millon, 46, was killed by police.
At about 6 p.m., Millon, who lived across the street, came through the house with a gun, went into the backyard and started shooting.
"The pressure got to him and he lost it. It was a matter of time, just to be honest and candid, it was a matter of time," said one neighbor who did not want to be identified. "It was horrible. It was about 30 shots last night. We were in our backyard and we hear everything going on, and it was a horrible scene."
Eventually, the incident ended up in the front yard, where police said the Millon executed both victims, firing several shots.
When officers arrived on scene, they confronted him and an officer-involved shooting occurred. Millon was shot by police and rushed to a hospital, where he later died.
From evidence at the scene, police said it was apparent that the suspect reloaded his weapon multiple times.
Neighbors said Millon and Bradford used to be in a relationship, but they said it ended with a case of domestic violence four years ago.
Millon lost his job because of the incident and moved away. He didn't move far -- he relocated just across the street.
"The fact of the matter is that the shooter was not stable. He had been dealing with issues since he lost his case of domestic violence, and I think that prompted everything that occurred last night," said the unidentified neighbor.
The neighbor said he knew Bradford and Millon. He said the couple was romantically involved and had a falling out. The neighbor also said Millon had problems with a court situation that may have led to an emotional breakdown.
Riverside Police reported that according to the California Department of Corrections and Rehabilitation Office of Public and Employee Communications, Arabella Bradford was a Parole Agent I with the California Department of Corrections and Rehabilitation. She began her career with CDCR as a Youth Correctional Counselor on April 1, 1997.
Malvin Conley was a CDCR Correctional Officer at California Institution for Men in Chino. He began his career with CDCR on July 25, 1993. He worked at California State Prison-Los Angeles County in Lancaster before transferring to CIM on December 6, 2004, according to Riverside Police.
Virgil Millon was a lieutenant with CDCR's Division of Juvenile Justice from April 10, 1987 to August 6, 2008. He began his career as a Youth Correctional Officer at the Heman G. Stark Youth Correctional Facility in Chino, according to police.
Anyone with information about the case is asked to call the Riverside Police Department's Robbery/Homicide Unit at (951) 353-7134.