Vegas Bray, 27, is scheduled to be sentenced Jan. 8 for the Oct. 16, 2012, death of Victor Saucedo.
Bray and the 31-year-old victim met while both were in the Navy. Their relationship lasted for several months and ended toward the latter part of 2011.
Prosecutors said the couple broke up because Bray was jealous of the mother of Saucedo's child, but the defendant continued to pursue the victim.
Bray committed seven acts of vandalism against Saucedo's car and apartment, including popping his car tires, smearing peanut butter on his door and even tracking him down after he changed apartments, said Deputy District Attorney Harrison Kennedy.
The couple talked about rekindling their romance the day before the murder, but Saucedo said he wasn't interested in the long-term relationship that Bray wanted, according to Kennedy.
Bray felt "spurned'' and left the victim's apartment the next morning, then returned in the afternoon with a gun and shot him nine times, police said. Bray called 911 after the shooting, saying Saucedo had committed suicide.