An incident early Saturday morning reminds Madison that it is not only residents and students that need to be aware of their safety but police officers as well.

Officer Kathryn Cherne was the victim of an alleged sexual assault at approximately 2:15 that morning as she and officer Stephen Heimsness were patrolling the 400 block of West Gilman Street.

Her attacker, 52-year-old Marvin Pierce, allegedly slapped her buttocks as the officers passed by him on the street, and as Cherne turned around to arrest him, he appeared to be grinning.

"I think the guy that did this is a criminal," Central District Operations Lt. Joe Balles said. "I mean this isn't a college student getting drunk and doing something; this is a predator against the downtown area that did this."

The alleged sexual assault was not the only offense Pierce committed that night, according to Balles.

"I don't know if he's got mental health issues, but apparently he held a knife up to someone," Balles said. "While we were searching, we also found the knife."

According to the criminal complaint, a nearby woman approached Heimsness shortly after Pierce was taken into custody. She told the officer that about an hour earlier, Pierce threatened her friend with a knife while they were waiting in line at Amy's Café.

Pierce allegedly approached the victim, pulled out a knife from his belt area and held it to the victim's throat. After the victim had stepped back and put his hands in the air, Pierce allegedly put the knife back into his front waistband and walked away.

Pierce allegedly returned only a few minutes later, however, and tried to spit on the victim. Pierce also allegedly put his hands in the victim's hair and pulled it.

The criminal complaint also stated when Cherne was searching Pierce, she not only found the knife but also a bag containing marijuana.

Balles said Pierce has been charged with fourth-degree sexual assault, second-degree recklessly endangering safety — a felony charge — and for outstanding warrants. He is currently being held in the Dane County Jail.

"I wish I could say he was the only kind of guy downtown like that," Balles said. "If these people show no respect for a police officer, then I ask, Who is safe in the downtown area?"

Balles encouraged all Madison residents to be cautious and to pay attention to their surroundings.

"That's why people have got to watch out for themselves downtown and work with us and point out any signs that just don't look right," Balles said. "This is a big town, and we have predators amongst us."

The criminal complaint also stated that Pierce is a repeat offender.