The driver of a stolen truck cab rammed three vehicles, including a police cruiser, yesterday during a wild chase in Maryland that ended when the suspect stopped short of barriers at an entrance to the grounds of the National Security Agency in Anne Arundel County, authorities said.

The driver's decision to exit the Baltimore-Washington Parkway in a restricted National Security Agency area briefly caused police and guards at the intelligence agency to be jittery about a possible terrorist attack.

"When he takes the ramp that goes to NSA," said Sgt. Thornnie Rouse, spokesman for the Maryland State Police, "then your flags really go up and you ask, 'Is he going to stop or not?' But I will say this: The officers on the other side of the fence were prepared to take the necessary action."

The man, whom police did not immediately identify, was arrested about 2 p.m. Rouse said authorities last night were still considering what charges to file against the man, who was described as being in his twenties. They said they were confident he is not affiliated with a terrorist organization.

The man and a Maryland State Police trooper were injured during the chase and transported to the Maryland Shock Trauma Center. The trooper, whose vehicle was rammed three times during the roughly 20-mile chase, was in serious condition last night, Rouse said. Police did not release his name.

The incident began about 1:40 p.m. when Baltimore police tried to stop the stolen truck cab. The driver, traveling at speeds approaching 70 mph, headed south on the parkway before turning onto Interstate 695. He then veered onto Interstate 95 and turned east toward Baltimore-Washington International Airport.

By then, about two dozen police cars from several departments were in pursuit.

Before reaching the airport, he turned north on Route 1, toward the Baltimore Beltway. On the beltway, he drove east toward Glen Burnie before heading south on the parkway.

At the parkway interchange with Route 100 near Jessup, the driver rammed a police cruiser that was trying to gain position in front of the truck cab, Rouse said. A few seconds later, the truck sideswiped a BMW. The driver of that car was not injured.

A few miles farther south, the truck sideswiped the police cruiser again, Rouse said.

As the chase continued, police tried to put tire spikes across the parkway near the exit for Route 175. But those plans were thwarted by another tractor-trailer that also was driving in the southbound lanes. "The trooper was in a position to throw the stop-sticks down and realized that was not the right vehicle," Rouse said.

The stolen cab hit the tractor-trailer, then struck the police cruiser for a third time -- this time hitting it from behind, Rouse said. Then the truck exited at the National Security Agency before stopping at the barriers.

"I think he just took the first ramp, not really knowing where it would go," Rouse said.

In Anne Arundel, rescue workers treat a man who authorities say drove a stolen truck and led police on a long chase.