JOLIET, Ill. (CBS) — A veteran Joliet police officer went into a library Wednesday and quickly found a suspect in the sexual assault of a 68-year-old woman.

As WBBM Newsradio’s Bernie Tafoya reports, the woman was returning to her car when she was sexually assaulted in a downtown Joliet parking garage in broad daylight Wednesday.

LISTEN: WBBM Newsradio’s Bernie Tafoya reports

“He unbuttoned her coat and began rubbing inside both above and below the waist,” Cmdr. Rich Demick said.

Police say her attacker hit the woman on the head and ran off off when someone saw what was going on in the parking garage between the 0-99 blocks of Ottawa and Chicago streets.

Witnesses ran to the attendant’s booth and had him call 911 after the 2:30 p.m. attack. The victim was bruised, but declined medical treatment.

Demick responded to the call and went down the alley and into the nearby library. He looked for a suspect described as wearing a red sweat shirt with dark sleeves.

Sure enough, he saw Matt Hooper, 17, peeping down the alley at the police activity outside. Hooper’s shirt matched the suspect description.

“I approached and asked who he was,” Demick said. “He gave a bogus name and acted very nervous.”

Hooper reportedly gave his real name when Demick said he didn’t believe him. Hooper agreed to walk outside, where he was identified by the witness, police said.

Hooper was questioned at the police station, and reportedly admitted fondling the woman and was arrested on charges of criminal sexual assault, aggravated battery and unlawful restraint.

Demick supervises the department’s Quality Assurance and Technical Services divisions. Downplaying his first arrest in some time, he said, “The area was saturated with officers. I just happened to be the first guy to check in the library.”

Joliet police Chief Mike Trafton disagreed.

“This is another example of Rich’s outstanding police work and the contribution he brings to the department,” Trafton said.

The Joliet Herald-News contributed to this report, via the Sun-Times Media Wire.