The body was discovered in a car parked at a Jack In The Box at the corner of Van Buren Boulevard and Trautwein Road on Jan. 17. Police say someone noticed a foul odor and called police.
The body has been identified as 24-year-old Gianni Belvedere. Authorities say Belvedere was the victim of a homicide.
Belvedere had been missing since Christmas Eve when his fiancée, 22-year-old Ilona Flint, and brother, 22-year-old Salvatore Belvedere, were found fatally shot outside a Mission Valley mall.
Police said in a news conference that they are searching for a "person of interest" described as a man about 5 feet 10 inches to 6 feet tall, wearing a black hoodie with "unique white bands around the sleeves up in the bicep area." He was also wearing tan pants and all white tennis shoes.
The man was believed to be in the Mission Valley Center Mall around 11:15 p.m. on Dec. 23, and then again around 12:15 a.m. Christmas Eve.