TINLEY PARK, IL — A Zion man died after witnesses reported seeing him fall to the ground during the Knotfest concert at Hollywood Casino Amphitheatre in Tinley Park Sunday night.

Richard Valadez, 62, of the 2300 block Galilee Avenue in Zion, was pronounced dead at 11:34 p.m., according to the Cook County Medical Examiner's Office. The cause of his death is not yet known, and an autopsy is pending, a spokeswoman for the medical examiner's office said. The circumstances of Valadez's death also are not yet clear. Tinley Park Fire Chief Forest Reeder said he did not have information because his department did not handle the emergency call.

"The Fire Department was not present for this incident at the amphitheater as the emergency medical services are provided by a private contractor for any on-site emergencies," he said.

Courtney Rourke, operations manager for Live Nation, did not respond to requests for comment. Live Nation is the amphitheater's venue operator.

However, distraught concertgoers at the heavy-metal music festival reported seeing Valadez suffer in distress while venue staff were slow and sometimes struggling to help him. Several attendees stepped in to try to assist the man and form a circle around him to keep the crowd from trampling him.

At first, witnesses said, Valadez appeared to be fine and to be enjoying himself while the music played. Levi Witvliet said Valadez stood next to him and his friend in section 206 of the lawn area and chatted for a while.

"He said he worked for Six Flags, and that he could get a deal for us," Witvliet of Lansing said. "But we didn't get a chance to get his number."

Brittany Ruel-Curtis of St. Anne, Illinois, said she watched Valadez, who was about 10 feet in front of her, chat up nearby people.

"He seemed fine throughout the concert, though, enjoying the music and drinks and talking to the people who sat in front of me," she said. As the night wore on, mosh pits formed in the lawn section, witnesses said, as they often do at heavy metal concerts. Valadez joined in some of them and was slammed around with the other moshers. He was knocked to the ground at least once, according to witnesses.