Police said community tips led to the speedy arrest.
"It's nice to know that we're taking back our streets, that we're able to make them safer for our kids," said resident Kathy Morales.
LAPD Rampart officers received a call of shots fired at Court St. and N. Bixel St. at 4:25 p.m. Tuesday.
According to police, four Hispanic men were at the top of the hill on Bixel when one of the men started shooting at a red Toyota Scion. The car fled the scene during the gunfire, but a child was struck.
The child, identified as Roberto Lopez Jr., was with his 6-year-old sister on his way to a neighborhood community center a couple of doors down when he was hit in the chest by a stray bullet.
Roberto was transported in critical condition to Children's Hospital Los Angeles, where he was pronounced dead.
Police believe the child was an unintended victim of gang violence.
Astorga had an extensive criminal history, according to police, and had served prison time for assault with firearms, burglary, grand theft auto, narcotics violations and other offenses. He had first been arrested at the age of 10.
Astorga does not live in the neighborhood, but he has reportedly admitted to being in the area at the time of the shooting.
He will be appearing in court on Tuesday.
Police said more arrests are expected.
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