William Thomas Forrer, a reputed drug courier and escape artist accused of abducting his infant son from a foster home in Anne Arundel County last month, was shot and killed yesterday at the airport in Sacramento, Calif., after he bolted from U.S. marshals who were trying to take him back to Baltimore.

Forrer was shot twice in the back by a deputy marshal as he ran through the airport parking lot, ignoring shouts to halt and appearing to outdistance his pursuer, according to Arthur F. Van Court, U.S. marshal for Eastern California.

Calling the shooting "an unfortunate thing," Van Court said, "This guy was extremely dangerous and had a record to prove it." If a deputy is convinced an escaping felon "is dangerous to the community . . . , " the marshal said, "you don't want him to get away."

After a nationwide search that followed the daring April 21 abduction, Forrer was arrested May 9 in Salinas, Calif., at the end of a wild car and foot chase.

During that chase, in which shots were fired and a police car was rammed, Forrer's left shoulder was dislocated, Van Court said.

He said Forrer wore a sling on the shoulder yesterday. A manacle on Forrer's right wrist was fastened to a chain around his waist. Because of the difficulty of climbing in and out of the van taking him and several other prisoners to the airport, he wore no leg restraints, the marshal said.

According to the account provided by Van Court and his deputy, David Stanton, Forrer was one of seven prisoners being taken from San Francisco to the airport.

On the trip, Forrer asked one or more times to stop at a restroom. His last request came at the airport, and a deputy from the San Francisco office, whose name has not been released, accompanied him to a restroom at a gasoline station there.

In the restroom, Forrer asked that his handcuff be removed. The deputy declined but broke the belt loops that held the waist chain, permitting Forrer greater freedom of movement.

On his way back to the van, "Just as he was ready to step into the front door, he whirled and pushed the deputy . . . and then took off running," Van Court said.

While a partner remained with the van, the deputy, "who was aware of what a dangerous background" Forrer had, ran after him, Van Court said. He shouted for Forrer to halt and then fired, but the fugitive got farther from him.

Van Court said the final two shots from the deputy's .357 magnum service revolver, fired from an estimated 100 to 150 feet, hit Forrer in the back.

"He was DOA dead on arrival by the time he hit the ground," Van Court said.

Authorities said Forrer was being returned to Baltimore to face a federal charge of unlawful flight to avoid prosecution in connection with the alleged abduction of his son.

According to authorities, Forrer, a Virginia man, left the baby on a Florida-bound airliner at Baltimore-Washington International Airport Feb. 21 with a diaper bag containing $35,000.

Authorities alleged that Forrer also left three bags of marijuana in the restroom of the plane, from which he fled when he realized he was under police surveillance.

Forrer's 9-month-old son, Zachary, became a ward of the state, and was cared for by a family in Pasadena, Md. Last month, Anne Arundel County police said, Forrer and another man used a gun to abduct a county social worker. She was then forced to lead Forrer to the foster family's home, where he obtained the child by posing as an FBI agent, authorities said.

The social worker later said Forrer had hit her and told her he would kill her and the foster family if they did not release the boy.

"I need my baby," Forrer was quoted as telling the social worker. "That's all I want."

The baby was in the van Forrer was driving when he was arrested this month in Salinas. The boy was treated for bumps and bruises and is now in the care of a state agency.

An FBI spokesman said Forrer is "known from New York to Miami as an alleged drug runner," has been convicted twice on stolen vehicle charges and has escaped from prison in Florida twice. According to the FBI, he also was wanted for assaulting a federal officer.

The baby's mother, Joyce Anne Klipa, 28, who was wanted in Maryland along with Forrer in the alleged abduction, was arrested May 1 by the FBI in San Diego.