A 16-year old Southeast Washington youth was shot and killed Saturday near his home as he was returning from an early Christmas shopping trip. He apparently was the victim of a robbery attempt.

D.C. police arrested three other 16-year-olds and charged them with homicide.

The victim, Donnell Plater, of 1448 Congress Pl. SE, was the second teen-ager to be shot to death on city streets in recent days. A 15-year-old Maryland youth, David Seaton, was fatally shot Thanksgiving Day as he sat in a friend's pickup truck stopped at a light at First Street and Michigan Avenue in Northwest Washington. There have been no arrests in that case.

Plater's 21-year-old sister, Laverne, said her brother was returning from a Christmas shopping trip when three youths spotted him in the 600 block of Lebaum Street SE. She said he backed away from the three, who had tried to take the packages, and was shot once in the back.

He did not know his assiailants, she said.

"He was just out shopping . . . just an innocent bystander," she said. "Donnell didn't know any of the kind of kids who would do a thing like this. He was a good boy -- respectful, honest -- he'd never been in any kind of trouble and neither had his friends."

She said her brother, the youngest child and only son in a family of four children, worked as a dishwasher in a downtown restaurant and was very thrifty with his money. "He probably had something special in mind and just wanted to buy it before the stores got too crowded," she said.

She characterized the Ballou High School junior as a friendly and funloving boy with many friends and no enemies. He was a serious student, who was interested in music, loved basketball and went to all the games, she said. He lived at home with their widowed mother, Helen.

"I still can't believe this has happened," Plater said in an interview yesterday. "He was a good boy and we were very proud of him. He was just walking down the street with a couple of paper bags, and now he's gone."