A Thornton police sergeant was slashed with a knife by a woman motorist after police found her slumped over a car steering wheel.

The sergeant, who was only identified as a 25-year veteran, was undergoing surgery for a deep laceration to his forearm at St. Anthony Central Hospital in Denver, police spokesman Matt Barnes said. He's in stable condition.

The bizarre incident happened after 10:51 a.m. when the sergeant and another officer tried to check on the woman who was unresponsive in the car parked outside a Wells Fargo bank in a shopping center at 12030 N. Colorado Blvd.

As the officers entered the car, suddenly the woman pulled a knife and threatened them, Barnes said.

The officers attempted to subdue the woman with an electric Taser stun-gun, but it didn't work, Barnes said.

The sergeant was able to knock the knife from the woman's hand with an Orcutt Police Nunchaku, a martial arts-like defensive weapon.

But as officers attempted to remove the disarmed woman from the vehicle, she grabbed another knife hidden in the car and "slashed the officer," Barnes said. "Then she drove away immediately, over the curb, over the lawn and out of the parking lot."

Other patrol cars surrounded the woman's car at 120th Avenue and Colorado Boulevard and she surrendered.

Aside from the knife used to stab the sergeant, police seized three more knives from the woman's car.

"We're unclear what the motive was," Barnes said of the woman suspect, a 54-year-old Thornton resident.

"We're unclear what state this female was in and what might have precipitated the attack on the officers," he added.

Police radio scanners captured the mid-day drama.

"I've got an officer that's been cut and a female now trying to leave," an officer radioed. "It looks like she's going to go northbound through the parking lot."

"I've got an officer who has been assaulted with a knife," the officer repeated.

The woman was taken to St. Anthony North Hospital for a medical evaluation, which is department protocol for anyone police use a Taser on, Barnes said.

After her release, she will be arrested on suspicion of first-degree assault on a police office.