After the fires were out and the people went home, the game changed from cat-and-mouse with tear gas to back-and-forth with accusations of police brutality.

“Officers displayed extreme restraint for the situation. Not just Ames officers, but the other law enforcement agencies present,” said Ames Police Cmdr. Jim Robinson. “They did follow the rules and regulations and showed extreme restraint.”

As officers battled rioters early Sunday morning, they began to use riot control techniques — including pepper spray, pepper gas and tear gas. Rioters were sprayed with pepper spray as they dispersed throughout the area.

As officers were moving people away from Welch Avenue down Chamberlain Street, officers sprayed individuals they believed were not moving.

“He’s not moving fast enough,” an officer told a man helping another person who was dealing with the effects of pepper spray.

Students’ accounts of the riots included stories of officers using riot-control substances on people who were not being unruly.

“We saw some guy right next to me get sprayed for no reason,” said Steve Freeman, junior in political science. “The reason was, he’s in the street.”

Crowds were asked to move by police as they pushed the crowd away from Welch Avenue.

“Move! Go home!”

Jaeger reiterated at the press conference law enforcement’s repeated attempts to ask the crowd to disperse.

“We continually told people this was an illegal gathering — they felt they had a right to be there,” he said.

Some students said they believed it was law enforcement officials who caused the crowds to go out of control.

“It was their aggression,” said Ryan Boeding, junior in marketing.

Ryan Rhodes, junior in horticulture, said too many officers were present, causing the crowd to react.

“It was provoked by an over-presence of police,” Rhodes said.

Phillip Gronewold, junior in psychology, said he believed police were harsh in forcing people into their homes.

“People were pretty much getting Maced everywhere on their lawn,” he said. “My roommate got it so bad his shirt is orange. They were pretty power-tripping last night.”

Jerry Stewart, director of the Department of Public Safety, said law enforcement agencies — ISU Police, Ames Police and the Story County Sheriff’s Office — acted appropriately.

“Actions taken by [law enforcement] were to deter escalation and prevent injury,” he said at a press conference Sunday afternoon.

— Tom Barton, Lucas Grundmeier and Emily Sickelka contributed to this article.