The shooting happened near Wilmington Park Elementary School on Monday just before 5 p.m.
"I thought it was fireworks," says 9-year-old Jackcel Fonseca.
He was on the playground when he heard the shots.
"I ran and got my backpack and went inside the cafeteria. So everyone went inside the cafeteria and we stayed there
His aunt Alejandra Sanchez picked him up from school Tuesday. She attended the school herself years ago, and is now very worried.
"It's dangerous," she says.
"Now you have to look around to see was next to you because you can't trust anybody."
12-year-old boy killed, 2 others wounded in Wilmington shooting
Police say the 12-year-old boy was in an SUV parked near the school with his 10-year-old brother and a 30-year-old woman who is a friend of the family.
Two individuals stepped out from behind some other cars and opened fire at the SUV multiple times, leaving it riddled with bullets.
The boy and the woman were both struck by gunfire and brought to a hospital. The boy was pronounced dead there.
On Tuesday, the county coroner's office identified the boy as 12-year-old Alexander Alvarado.
His 10-year-old brother was not injured.
The woman remains in critical condition.
Police do not know a motive behind the shooting and have not released a description of the suspects.
City officials are vowing to find those responsible.
"We will find you," said City Councilman Joe Buscaino. "We will hold you accountable. Letting these criminals walk scot-free is akin to saying that these victims' lives do not matter."
A 9-year-old student was struck by the stray bullet while she was out on the playground during an afterschool program.
About 60 students are a part of the program, but she was the only one hurt and taken to the hospital.
Police said the girl suffered critical injuries.
One mother told ABC7 on Tuesday her daughter, who's in the fifth grade, is a part of the same afterschool program.
"I wasn't able to get her, you know? It was scary not knowing when you hear there's a shooting," said parent Kalena Guimary.
Some parents were dropping their children off to school themselves to guard their safety.
"I asked to come in an hour late to work," said parent Amber Martinez. "I never drop them off. It's always my dad, but [Tuesday,] I kind of had to pull them out of bed. They didn't really want to come."
Some parents said explaining what happened to their kids is difficult.
"My niece was kind of in shock because she didn't want to believe it either because it's her school," said Regina Romero, who takes her niece and goddaughter to school. "She's been here since preschool, and she felt kind of scared coming to school [on Tuesday.]"
Martinez said she took time to explain to her children about the severity of the incident.
"I had to tell them like, you know, it's only this time," she said. "It's maybe not going to happen again, and then they're like, 'Maybe I don't want to play on the playground.'"
Further details regarding the suspects have not been released. Investigators only said they believe the shooters took off in a vehicle.
Meanwhile, officials said extra security will be around the school and counselors will be available for students and staff.