A 17-year-old boy was killed and two men were critically wounded in a shooting on Tuesday morning in the Back of the Yards neighborhood on the South Side of Chicago.

Police said, at 7:40 a.m., a dark SUV pulled up in the 5000 block of South Throop Street, when someone in the vehicle got out and started shooting, hitting a 17-year-old boy who was walking outside and two men – ages 55 and 61 – sitting in a nearby vehicle.

The 17-year-old was taken to Comer Children’s Hospital, where he was pronounced dead. Both men were taken to Stroger Hospital in critical condition.

Dozens of shell casings could be seen in the street after the shooting.

One witness, who asked to remain anonymous, described the shooting.

“It was just so loud, so loud and so many, and I’m just like, ‘What is that?’ and my son was like, ‘That’s gunshots, get down!’” she said. “I saw them pick up the backpack. He was laying. They were doing CPR.”

The shooting happened just a few blocks from Peace and Education Coalition High School, an alternative high school for youth between ages 16 and 21, although it was not clear if the teen had any connection to the school.

The two men who survived the shooting drove to a nearby auto repair shop, where one of the workers, who asked to be identified only as Leo, saw them pull up in a red minivan.

“I thought it was a customer needing a tire repair, and when they pulled up at window level, the driver said, ‘I need assistance. Can you call paramedics?’ And I did so,” he said.

The minivan’s rear window had been shot out. Leo said the men’s injuries looked severe, and he acted quickly to get help.

“There’s just no time to overthink it. Just act upon it right away. Get some help,” he said.

About a mile and a half away from the shooting, police were seen investigating an SUV near 44th and Wolcott, where an AK-47-style assault rifle was lying on the ground nearby.

No one was in custody Tuesday afternoon. Area 1 detectives were investigating.