The Cook County Medical Examiner identified the person who died as Benjamin Seto, 24, of Falls Church, Virginia.
The city's Office of Emergency Management and Communications said the attendee was taken from the event in critical condition Saturday night and died at a hospital. The circumstances around the death are still being investigated.
RELATED: Video shows dozens of people jumping fence at Grant Park
Last year, a 16-year-old died after being found unresponsive at Lollapalooza and around 280 people were sent to the hospital. This year's numbers have not yet been released.
Crews began their cleanup process after the festival wrapped at 10 p.m. Sunday.
Another consistent issue this year were the dozens of people breaking down the exterior barrier of Lollapalooza, trying to make their way into the festival for free, despite added security measures. The festival and CPD added security on Friday after video of 50 people storming the barrier was posted to social media.
Two teens were also arrested Sunday at Lollapalooza for allegedly punching a police horse.
The boys, 15 and 17, were among a group that was threatening each other and beginning to fight in the 400 block of South Michigan Avenue, according to Chicago police.
A CPD mounted unit officer tried to break up the scuffle about 7 p.m. by placing his horse in the middle of the group, police said.
The 17-year-old then punched the horse in the face, police said. When the officer tried to detain the teen, the 15-year-old stepped forward and also punched the horse.
Officers arrested the older boy at the scene, according to police. The younger boy ran away, but was arrested by a bike unit in the 100 block of East Van Buren Street.
They were both charged with a single misdemeanor count of "teasing, striking or tampering with a police animal," police said.
Grant Park was packed over the weekend, with roughly 170 performers taking eight stages.
Festival-goers like Michelle Mirzoian said they were enjoying themselves on the festival's final day.
"I've been doing this for 10 years with some of my friends so clearly, always want to come back for more," Mirzoian said.
"My experience has been nothing but wonderful," said Dawson Kemme, who attended the festival Sunday. "This is the best time of my life. I can't wait to come next year."
The Associated Press and the Sun-Times Media Wire contributed to this story.