A mortgage banker in this affluent Baltimore suburb was shot and killed last night, apparently when his 3-year-old son picked up a loaded handgun and shot him before his mother could stop him.

Baltimore County police said today they consider the death of James Sloan Calwell IV, 35, "an apparent accident."

James Calwell, his wife Brenda, 33, and their son, Christopher, had just finished eating a pizza in the master bedroom of their home at 2 Trelawny Ct. when the accident occurred about 6:45 p.m. Sunday, police said.

Brenda Calwell told police she left the room to clean the dishes, and her husband took off his clothes to take a nap, according to police spokesman Paul Waclawski.

Calwell said that when she returned to the room, she saw the couple's son, Christopher, standing by the bed and holding James Calwell's .38-caliber snub-nosed revolver, Waclawski said. He said Brenda Calwell told police that she ran around the bed and came up behind her son.

"She said she was just reaching for the gun when it discharged," Waclawski said.

James Calwell, who was shot in the back of the head, was pronounced dead at the scene.

A bag of children's toys lay today outside the front door of the Calwell home, and a chorus of yelping dogs was the only answer to the doorbell.

Drivers slowed as they passed by the yellow-shingled, ranch-style house with a back-yard pool, set on a quiet cul-de-sac, and neighbors stopped each other to share snippets of information about the Calwells, private people whom they had seen only occasionally, when James Calwell washed his white Buick Riviera, or Brenda Calwell mowed the lawn, now slightly shaggy and dotted with dandelions.

"They were inside all the time. They hardly talked to anyone," said Chintha Kuruppunagake, a neighbor.

Waclawski said police probably would question Brenda and Christopher Calwell again after the funeral.

He said it was not clear whether the boy had picked up the gun from the floor or from a nightstand next to the bed, or why James Calwell had a gun.

Waclawski said there are no state laws governing the use of handguns inside the home, and that Christopher Calwell is too young to be charged with any crime under state law.

A spokesman for Calwell's firm, Larson Mortgage Co. of Essex, said Calwell, a Baltimore native, had been with the firm for about 1 1/2 years and had been in the banking business for about 15 years.

Brenda Calwell and Calwell's mother, Marie, contacted by telephone, both declined to talk about the incident. "I have enough heaviness in my heart already," Brenda Calwell said.