The boy, identified as 10-year-old Calvin Santos, later died at a hospital.
Witnesses say if the driver had been drinking, he may have been spooked by a Chicago police car that rolled up behind him. Seconds later, the driver swerved into the row of parked cars, causing the chain reaction that killed the boy.
"I can't say nothing. I just want my son back," said Bulmaro Santos, the boy's father.
"Nothing is going to bring my cousin back," said Dania Soto.
Calvin Santos had just watched his sister jump out of the family's car and head for the curb before the accident happened. As he followed, a crash down the block reportedly pushed several cars forward, crushing him.
"The police car was behind him, and we guess he was drunk or drinking and he got nervous or something and pulled over," Soto said tearfully.
"I think he was drunk because I tell him, 'You hit my baby,' and he not even listen to me."
The details are devastating to Calvin Santos' family. Bulmaro Santos was dropping the boy and his sister off at a relative's house so he could go to work. Several family members witnessed what happened. So did another woman, Anna Jorge. Witnesses say the father's car was double-parked.
"I turn around and look to the window and see this little girl screaming. Everyone was screaming, and I just see a little boy," she said.
"If he's not charged, he got away with murder," family friend Matthew Henderson said.
Calvin Santos was being remembered Saturday afternoon as a friendly and playful boy who loved wrestling. He had just turned 10 years old. But on Saturday night, relatives were planning a funeral, instead of his birthday party.
"We were so excited," said Soto. "He was going to be part of it. He was going to dance with me."
Police confirm alcohol is suspected in the crash. Detectives say they interviewed the driver all day Saturday, but no charges had been files as of Saturday evening.