A Martinsville police officer fatally shot a 61-year-old man who authorities said pulled a knife on a grocery store clerk, stabbed a police car, led officers on a two-mile chase and ignored four high-voltage Taser darts before attacking another officer with the weapon.

Donald Barry Minter of Martinsville died at Memorial Hospital of Martinsville and Henry County after the showdown Thursday afternoon, City Manager Clarence Monday said.

"At this point and time I have every reason to believe the officers acted in an appropriate and professional manner," Monday said in a statement.

Police were summoned to the Kroger on Commonwealth Boulevard just after noon for a report that a man had threatened a store clerk with a knife, Monday said. The city manager said it wasn't clear whether Minter drew the knife for a robbery or another reason.

When officers arrived, Minter was in the parking lot. He charged a police cruiser, stabbing the driver's side window repeatedly, Monday said. Another officer shot Minter with high-voltage stun gun darts, but he apparently wasn't fazed. Minter retreated to his own car and locked the doors, Monday said.

An officer broke the car window and blasted Minter again with Taser darts. Again, he was unaffected. He backed over a shopping cart, brushing a police officer's leg, and sped off, Monday said. The officer was unhurt.

Police chased Minter about two miles into Henry County, where Minter crashed into a fence, Monday said.

Officers blocked his car and ordered Minter to stay put. Instead, he got out and ran behind the Sportlanes Bowling Center on Koehler Road.

Officers followed and Minter pulled the knife again, Monday said.

Police shot Minter twice more with Taser darts -- again without effect, Monday said. Minter advanced toward a nearby officer, Anita Sowers, and drew back the knife, Monday said. Another officer, "fearing for their lives," opened fire, striking Minter, the city manager said in a statement.

Monday wouldn't release the name of the officer who fired the fatal shot.

"I just don't feel it is fair to the officer," he said.

Monday, a paramedic, happened to be nearby when the shooting happened and gave Minter CPR until an ambulance arrived.

"It's really unfortunate it had to come down to something like this," he said.

Minter's family could not immediately be reached.

Virginia State Police are investigating.

In addition to the circumstances of the killing, the investigation will consider why stun gun darts failed to subdue Minter.

Officers are trained to shoot Taser darts from a range of 7 to 15 feet, aiming at two muscle masses, such as the torso and leg, said Steven Tuttle, a spokesman for Taser Inter- national Inc. in Scottsdale, Ariz.

The stun gun, connected by wires to the darts, is less effective when the probes hit areas of the body with less muscle, Tuttle said. Both probes must embed in flesh to create a circuit for paralyzing high voltage, he said.

If only one probe hits, the Taser won't work, and if the probes land too close together, the shock is painful but not debilitating. Clothing also can affect the darts, Tuttle said.

"There's a lot of different factors that play into it," Tuttle said. "It's clearly not a magic bullet."