CHICAGO (AP) _ A man charged in three sniping incidents since 1981 told police he was sorry that the most recent case involved ''someone so young'' - a 7-year-old boy killed while walking to school with his mother.

Anthony Garrett, 33, of Chicago said he accidentally hit Dantrell Davis in the head while aiming at teen-agers he thought had been shooting at his building, police said.

Garrett - who was acquitted in a 1981 sniper death but served time four years later for a shooting in which no one was hurt - was charged Wednesday with murder.

During his confession, Garrett ''appeared very remorseful about shooting the boy and said he felt guilty about shooting someone so young,'' Lt. Rich Stevens said.

Police said Garrett took an automatic rifle equipped with a scope to the 10th floor of a sparsely occupied building in the Cabrini-Green public housing complex on the city's North Side.

Garrett, who said he wanted revenge on local gang members, fired about three shots at a group of teen-agers, saw someone fall and then fled, said Belmont Area police Commander William Callaghan.

Garrett was scheduled to appear in court Friday for a hearing.

Davis was the third student at the Jenner Elementary school to be shot and killed this year. On March 3, a second-grade boy was killed outside a high- rise building adjacent to the one where Davis lived. Only a block away, on July 23, an eighth-grade girl was shot and killed.

More than 120 children ages 2 to 18 have been shot and killed in the city this year, according to police.

Garrett served six months in prison for an aggravated assault charge in 1984 and 50 days in jail in 1985 for unlawful use of a weapon in a sniping in which no one was injured, police said. He also served time in 1987 on a weapons charge.

In the 1981 murder case, witnesses did not show up to court and jurors acquitted Garrett for lack of evidence, Zuley said.