Tom Carideo said he was driving to pick up his young children around 8:10 p.m. near the North Coast Music Festival at Union Park when he spotted the naked man running around, the Chicago Tribune reported Monday.
"This guy was literally running in circles naked as the day he was born," Carideo said. "Then he looks at my car and goes into a full-out sprint and jumps, landing ass first on the right side of my windshield and shatters it."
Carideo said he armed himself with a hockey stick from his car in case the man attacked him and he called 911. He told the dispatcher the naked man had smashed his windshield and was bleeding from his buttocks.
Carideo said he stayed on the line with dispatchers and followed the man in his car. He said the naked man danced in the middle of an intersection before drinking the water from a puddle in the street.
Carideo said police had to use a stun gun on the man at least once to subdue him.
Police said the man, Sam Schauer, 22, of Auburndale, Mass., was charged with reckless damage to property, resisting/obstructing police, reckless conduct, aggravated assault and public indecency. He is due to appear in court Sept. 27.
Police said they suspect Schauer was under the influence of a hallucinogenic substance at the time of his arrest.