Salvador Esparza, of Monrovia, was killed during shooting at a home in the 300 block of Figueroa Drive the night of July 5.
Investigators said family and friends were sitting on a porch when a man walked up and fired at least 13 shots before fleeing in a black car.
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Salvador and a 27-year-old man were struck by bullets. Both were taken to the hospital where Salvador succumbed to his injuries.
The boy was looking forward to starting kindergarten this year, officials said.
More than seven weeks later, investigators said they have leads, but no suspect.
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It was announced Thursday morning that a $20,000 reward was being offered for information leading to the arrest and conviction of the suspect responsible for Salvador's death.
Anyone with information about the shooting was urged to call the Los Angeles County Sheriff's Department's Homicide Bureau at (323) 890-5500.
Those wishing to remain anonymous may call Crime Stoppers at (800)222-8477.