When a taxicab drifted down a block of a Northeast street early yesterday and came to a crashing halt, passersby thought the driver had had a heart attack. They were horrified when they took a closer look and saw that he had been shot in the back of the head, police said.

One of the people used a cell phone to call an ambulance, but it was too late. Beautford Garrett, 56, of the 3200 block of Curtis Drive in Temple Hills, was pronounced dead at D.C. General Hospital minutes after the 1:15 a.m. shooting, police said.

It was the fourth serious incident involving a D.C. cabdriver in six months. A driver was stabbed to death in November; another was stabbed and robbed that month. In August, a driver was paralyzed after being shot once in the head during an apparent robbery attempt.

In yesterday's incident, the Madison Cab Co. taxi came to a stop in a parking lot at East Capitol Street and Anacostia Road NE after sideswiping parked cars, police said.

"He was not on a radio-dispatched call, so he must've picked him up on the street," said Melvin Sydnor, a co-owner of the cab company, so it was impossible to know what happened just before the shooting. "We have no idea how it happened or why," Sydnor said. Garrett had not been robbed, he said.

He said only one of his drivers has a bulletproof partition in his cab. The other drivers prefer to avoid what Sydnor called the staggering cost of such a device--prices at one dealer start at $395, not including installation. Drivers also say the partitions impede the flow of warm and cool air.

Meanwhile, the police scanner crackled yesterday morning with a complaint from a passenger who was passed up by a taxi. Because of the most recent attack, more passengers will be passed up more often, Sydnor said.

"The police give us tickets if we don't pick people up," he said. "But now they have to investigate a murder because we pick everyone up."

Police are passing out fliers asking anyone who saw anything suspicious or unusual to call 6th District detectives at 202-727-4515, or Crime Solvers at 800-673-2777.