Two people were killed and two others were wounded in a shooting early Thursday at a Back of the Yards neighborhood block party on the South Side, and a teenage girl who witnessed the shooting suffered an asthma attack and later died.

At 12:18 a.m., an altercation broke out in the 800 block of West 50th Place, and someone started shooting, according to Chicago Police.

Denzel M. Childs, 25, was shot in the neck, head and chest; and was taken to Stroger Hospital, where he was pronounced dead at 1:20 a.m., police and the Cook County medical examiner’s office said. Childs’ home address was not known Thursday morning.

Kayana Q. Armond, 34, was shot in the neck and was also pronounced dead at the scene at 12:34 a.m., authorities said. She lived in the 10900 block of South Vernon.

A 21-year-old woman suffered a gunshot wound to the left hand and was taken to St. Bernard Hospital, while a 25-year-old woman was taken to Stroger Hospital with gunshot wounds to the back. Both of their conditions stabilized, police said.

Jessica Williams, 16, witnessed the shooting and suffered an asthma attack, authorities said. Williams, who lived in the 12000 block of South State Street, was taken to St. Bernard Hospital, where she was pronounced dead at 2:05 a.m.

The crime scene on West 50th Place stretched from Peoria to Halsted. Dozens of people, ambulances and about 15 squad cars were scattered along the street early Thursday. A man could be seen crying and walking away on Halsted with a female and two officers.

A woman, who preferred to remain anonymous, claimed to be the aunt of the 25-year-old woman who was shot. She said the party was a memorial for a friend who was shot to death about four years ago. About 75-100 people were at the party outside, grilling food and drinking.

She was across the street when she saw a man and someone else arguing.

“It was like someone who was from over here arguing with someone who probably wasn’t from over here,” she said.

She said as other people got involved, the first man pulled out a gun and fired into the air before more people started shooting. She later saw the man getting rolled away into an ambulance.

“When I saw him pull the gun, I ran to a porch … and chilled there until it was safe,” she said. When the shooting stopped, she “heard everyone hollering ‘this person got shot and this person is shot and this person is shot’.”

She said her niece is a mother of four and a hard worker.

Another partygoer, James Hughes, said the shooters were part of a faction of the Almighty Black P Stone gang called the Moes, who “saw a fight break out and they fed off it.”

When the shooting started, Hughes said he saw more than 50 people try to run away. He took to the ground and tried to shield a friend whose “brother and father are already gone.”