Known as one of the most gun violent cities in America, Chicago recently marked a new grim milestone with 18 homicides in a single day, officials said.

On Sunday, May 31, the Chicago Police Department responded to the most homicides in a 24-hour period, Max Kapustin, senior research director of the University of Chicago Crime Lab, confirmed to ABC News.

Kapustin said the day also capped the deadliest weekend residents in the so-called Windy City have seen in 28 years. According to his lab’s data, which goes back to 1961, the previous record for the most homicides in a single day was 13 on Aug. 4, 1991.

In fact, there were so many autopsies to do on June 1 that Chief Cook County medical examiner, Dr. Ponni Arunkumar, had to call in additional pathologists to complete them all. The medical examiner’s office conducted a total of 35 autopsies on that day, including 15 gun-related homicides, a spokeswoman for the office told ABC News on Tuesday.

“This is an unprecedented amount of homicides in one day for our office,” Arunkumar said in a statement. “The most I can recall in one day since I started here in 2003 is 10.”

Natalia Derevyanny, a spokeswoman for the medical examiner, said the victims ranged in age from 18 to 39.

Between 6 p.m. on May 29 and 11:59 p.m. on May 31, Chicago police responded to at least 73 incidents in which 92 people were shot, including 27 who were killed, according to the city’s police department.

The medical examiner’s office said it conducted autopsies on additional victims who died over that weekend in Cook County outside the city of Chicago.

The first homicide in Chicago on May 31 occurred at 12:37 a.m. in the city’s West Engleside neighborhood, according to police. In that episode, a 36-year-old man died after a vehicle pulled up to him. He was fired at multiple times, with bullets hitting him in the chest and leg, according to a police report. No suspects have been arrested.

Other victims gunned down on May 31 included two teenage students.

Lazarra Daniels, 18, a student at DRW College Prep high school in Chicago, was shot in the head about 10:51 p.m. in the city’s West Garfield Park neighborhood. Police discovered her body after responding to a ShotSpotter alert.

Tony Sutton, the principal at DRW College Prep, announced Lazarra’s death in a post on the school’s Facebook page.

“Lazarra was quiet, funny, and got along well with her peers and teachers,” Sutton wrote. “This is an incalculable loss for her family, and one that will pain those who loved Lazarra for a long time.”

Also killed was 18-year-old Keishanay Bolden, who was majoring in law enforcement and justice administration at Western Illinois University and planned to be a corrections officer, according to a tribute posted on the school’s website.

Bolden was shot in the torso about 4:25 p.m. on Chicago’s South Side after she got into an argument with a man, who fled the scene in a dark-colored sedan, police said. She was taken to a hospital, where she was pronounced dead.

“Keishanay always had a smile on her face and a contagious laugh. Not only was she fun to have in class, she was dedicated to learning and her community. This is tragic,” Rebekah Buchanan, an English professor at Western Illinois University, wrote on the school’s website.

Buchanan shared an essay Bolden wrote as a class assignment about the Chicago neighborhood where she grew up and was killed.

“Englewood community — I have been living here since I was young. It’s basically family,” Bolden wrote. “We all come as one whole battlefield and we went through the same struggle, knowing we all grew up around violence and police brutality. Still, we remained as a family even though we have disagreements, and when one person is hurt everybody is hurt. We all might not hurt the same but we can feel that pain when one of ours is hurt. Everybody has the same struggle because we all try to pitch in and help each other as a whole big family.”

The deadly streak in Chicago came a week after 49 people were shot in the city, 10 fatally, during the Memorial Day weekend.

Chicago Police Superintendent David Brown said at a May 26 news conference that the violence marked the most shootings for a Memorial Day weekend that Chicago has seen since 2015.

He blamed the resurgence of gun violence on disputes between rival gangs, clashes involving the sale of illegal drugs and people “feeling restless after being cooped up for weeks” due to the coronavirus.

“The violence throughout the city on Memorial Day weekend was nothing short of alarming,” Brown said at the news conference.

ABC News’ Joshua Hoyos contributed to this report.