The shooting occurred at 2:26 p.m. Sunday in the 11300 block of Hatteras Street, according to Los Angeles police.
Authorities identified the shooting victim as Roberto Fletes, 42, of North Hollywood. Police said he died at a hospital.
After the shooting, authorities say the gunman kidnapped his ex-girlfriend, identified as 31-year-old Jenny Marie Downes.
Police say Downes and the suspect, identified as 37-year-old Shane Winfield Rayment were in an argument near the intersection and Hatteras Street and Tujunga Avenue.
Person stabbed at Carl's Jr. in North Hollywood, suspect arrested after chase on 5 Freeway
Suspect in custody after stabbing at Carl's Jr. in North Hollywood
Fletes tried to intervene and was shot by Rayment, according to police. The alleged gunman then forced his ex-girlfriend into a truck and fled the scene.
A crime alert was issued for Rayment. Also listed in the alert were four people believed to have accompanied by him -- a 30-year-old white man, 5 feet, 9 inches tall, 170 pounds, with long blond hair, blue eyes, a black shirt and blue jeans; and three white female suspects with no further descriptions.
The suspects' vehicle was described as a green four-door pickup, possibly a Dodge Ram.
Anyone with information was asked to contact Valley Bureau homicide detectives at 818-374-1923 or the Department Operations Center at 213-484-6700. Anonymous tips can be left at Crime Stoppers, 800-222-TIPS (8477).
City News Service contributed to this report.