An 18-year-old was found mortally shot early yesterday in Northeast Washington inside a car stolen last weekend from the driveway of a U.S. Secret Service agent in Maryland, police said.

Police said residents called 911 to report a shooting in the 500 block of 47th Street NE about 2:10 a.m. yesterday. Officers found Joshua N. Arrington unconscious behind the wheel of a black Chrysler Concorde, police said.

Arrington, of the 4200 block of Clay Street NE, was taken to Washington Hospital Center, where he died about three hours later.

Police said they believe a gunman approached Arrington, fired several shots through the car's closed window and then drove away in a white Mercury Marquis.

The Concorde, a Secret Service take-home car, had been reported stolen Saturday to Prince George's County police from the home of an agent in Oxon Hill. Police say they suspect that Arrington stole the vehicle.

Arrington's relatives could not be reached yesterday. Police officials said the shooting appeared to be drug-related but released no other details.

Cmdr. Robin Hoey of the 6th District, where the shooting occurred, said officers were canvassing the area and intensifying patrols to gather more information.

The shooting came just hours after D.C. officials announced a stepped-up effort to combat an increase in auto thefts committed by teenagers. Four people have died in wrecks caused by juvenile car thieves in recent weeks.

Mayor Anthony A. Williams (D) announced a plan Monday night that includes increasing cooperation between police and prosecutors in car theft cases; improving recreation facilities for youth; installing street barriers and other traffic-slowing devices; and requiring more parental involvement with children accused of auto theft.

D.C. police have also declared a limited crime emergency, suspending some labor rules for about 350 officers to allow commanders the staffing flexibility to better target auto theft and other crimes committed by juveniles.

Police are offering a reward of as much as $25,000 for information leading to the arrest and conviction of a suspect in yesterday's shooting. Police urge anyone with information to call 202-727-9099.

Yesterday evening, in another incident that apparently involved at least one stolen car, four suspects, two of them believed to be juveniles, were taken into custody in Virginia after being pursued there by D.C. police, authorities said.

The four were taken into custody about 7:45 p.m. after the car they were in crashed exiting the Woodrow Wilson Bridge into Alexandria, Alexandria police said.

Authorities said that the car had been pursued on the Capital Beltway after an armed robbery and two carjackings.

D.C. officials said the first carjacking occurred about 3 p.m. in the 3800 block of Stanton Road SE.

Authorities said the suspects in that incident were being investigated in connection with a robbery in the Iverson Mall area of Prince George's County and a second carjacking in the District, on Chesapeake Street SE about 6:45 p.m.

The second carjacking reportedly touched off the chase that ended in Alexandria, officials said. According to a police account, the four suspects were being held last night as fugitives from the District.

Staff writer Martin Weil and staff researcher Bobbye Pratt contributed to this report.