An off-duty sheriff's deputy shot and killed a man who was alleged to have slain two people in Fontana on Saturday night, according to authorities.

In a statement, the Fontana Police Department said officers responded to the Falcon Ridge Town Center shopping area at about 9:40 p.m. after it was reported that shots were fired.

Two people, a 43-year-old man and a 40-year-old woman, were shot. An off-duty law enforcement officer witnessed the shooting, police said, and shot the suspect.

The suspect, identified only as a 45-year-old man as of Sunday morning, was pronounced dead at the scene.

The two victims, who also remain unidentified as of Sunday morning, were pronounced dead at a local hospital.

Investigations into the incident remain ongoing. As of Sunday morning, it was not yet clear if the suspect and victims knew each other or what led up to that initial shooting. It's also unclear how the officer-involved shooting occurred, or if the suspect fired shots at the officer first.

No additional details were immediately made available. Fontana PD told CBS News Los Angeles that the off-duty officer is a deputy with the San Bernardino County Sheriff's Department. They did not identify them or indicate if they suffered any injuries in the incident.