The car was parked at a Jack In The Box at the corner of Van Buren Boulevard and Trautwein Road. A man's body was discovered around 12:30 p.m. when someone noticed a foul odor and called police.
Authorities have not identified the body, but they say the license plate number of the car matches that of a vehicle that has been missing for more than three weeks, according to San Diego police.
On Dec. 24, 22-year-old Salvatore Belvedere and 22-year-old Ilona Flint were found shot to death in a vehicle outside a Mission Valley mall. San Diego police say that since that incident, they have been looking for Salvatore's brother, 24-year-old Gianni Belvedere, along with a 2004 dark green Toyota Camry with the Utah license plate B154VZ.
The car found in the Riverside parking lot matches the description of the missing vehicle. Authorities say the body was so badly decomposed that they don't have a cause of death yet. But they say it does look like a homicide.
Positive identification of the body is pending. San Diego homicide detectives have arrived in Riverside and are working with Riverside police on the case.