Police said an argument led up to the crime, which happened around 1:10 p.m. on Oct. 19 in Cambodia Town.
Long Beach Fire Department paramedics took the victim to a hospital, where he died, police said.
Police are asking for witnesses to come forward. Specifically, investigators think there were multiple people who took off right after the shooting happened.
Authorities believe the gunman was trying to rob 20-year-old Guy Alford III, who was a beloved member of the LBCC Vikings football team.
The 18-year-old victim was on the sidewalk on 69th Way when a group of three people came around the corner at Muriel Avenue and confronted him, neighbors said.
Police said the killer and the victim “were arguing over their involvement in the illegal gambling establishment” before the deadly shooting on Aug. 22.
Detectives responded about 9:10 p.m. Thursday to a gunshot victim call in the 1600 block of West 105th Street, near Denker Avenue, where they located the victims, authorities said.
Police are treating the killing as an act of self-defense.
A Long Beach man was arrested on suspicion of the murder, while a woman was arrested for allegedly hiding evidence to protect him.
Long Beach police said they found a rifle believed to be the murder weapon near where they arrested Darral Frank in San Pedro around 3:15 p.m. Sunday.