Two men shot and killed each other Monday morning after one of them ambushed the other while he was with his 18-month-old son in Chicago Lawn on the South Side, police say.

Alton D. Ellis, 31, was with his toddler about 8:40 a.m. in the 6200 block of South Mozart Street when Rayshawn Finley, 24, approached him on foot and fired shots, Chicago Police and the Cook County medical examiner’s office said.

Ellis was struck in the chest and twice in his torso, and fired shots in return, police said. The toddler was unharmed.

Police initially said Ellis was taking his son to school when the shooting happened, and his son ran to get help. They later said that a 23-year-old woman heard the gunshots from inside her apartment and found Ellis outside with gunshot wounds.

Finley, who allegedly fired shots first, was struck in both of his thighs, police said. He lived in Chatham.

Officers responded to the gunfire and found Finley in a car with gunshots and applied a tourniquet, police said. He was taken to Christ Medical Center in Oak Lawn and pronounced dead.

Ellis, who police said was targeted for “unknown reasons,” was taken to Holy Cross Hospital and also pronounced dead. He lived in southwest suburban Justice.

Arturo Rodriguez was at home in his bedroom when he heard the gunshots.

“They came in three waves,” Rodriguez said. “All I heard was ‘boom, boom, boom,’ and then a woman screaming and a kid crying.”

Rodriguez thought the shooting happened a block east on California Avenue, but his son told him it was in their back alley.

“I looked out my window and saw a guy lying down in the alley,” Rodriguez said. “The woman was screaming and pulled him into the garage.”

Another neighbor, who asked to remain anonymous, said he saw about a dozen evidence markers as police investigated the shooting.

By Monday afternoon, remnants of yellow police tape were strewn at the alley’s north entrance on 62nd Street behind Mozart.

A trail of bloodstains and several bullet holes in one of the garage doors down the alley marked where the shooting had occurred.

Less than two blocks east of the scene, Stephanie Roberts and other Chicago Public Schools parents were picking their children up from the nearby Fairfield Elementary School. She said her two children were already in school when the shooting happened, but it scared her that it happened so close.

“It’s dangerous because we’ve got so many kids walking to and from school by themselves,” Roberts said. “Me and my kids don’t walk that way anymore because the block isn’t safe right now.”

A staffer at Fairfield, who asked to remain anonymous, said the shooting happened less than an hour into the school day.

“We tried not to let the kids find out, but they heard the shots so they knew,” he said. “Sadly, it was just another day in the neighborhood to them.”

He said he heard about 15 gunshots and then helped make sure all the school’s doors were locked.

“Kids should be able to come to school and not worry about shootings,” he said.

Area Central detectives are conducting a homicide investigation.

Contributing: David Struett