Police said yesterday they have charged three former students of a prestigious Alexandria boarding school in the killing of a cat belonging to the dean of students and his wife.

All three were students at Episcopal High School when the incident occurred at the school in June, said the headmaster, F. Robertson Hershey.

"It's a reprehensible act, which is clearly way beyond the standards that we will tolerate," Hershey said. "Initially, it was thought to be a prank, and it spontaneously ended up to be something much more horrific."

Police said the cat, named Bella, was placed in a pillowcase, beaten with a baseball bat and then buried in a wooded area of the campus.

William Graham, 19, of North Myrtle Beach, S.C., has been charged in warrants with cruelty to animals and petty larceny. Each charge carries a maximum penalty of a year in jail.

Graham could not be reached for comment yesterday. Hershey said he graduated from Episcopal High and is attending college this fall.

The other two youths, both 17, were not identified by police because they are juveniles. Alexandria police spokeswoman Amy Bertsch said one of them, a resident of Miami Beach, Fla., was charged with cruelty to animals and petty larceny, and the other, who lives in Front Royal, was charged with petty larceny.

Police Detective Dana Lawhorne said the Florida youth was the "main aggressor" in the group and later told his mother what had happened.

"He and his mother came here from out of state to confess to the headmaster," said Lawhorne. "He and his mom did the right thing. They wanted to get it off their chests.

"It was an end-of-the-school-year prank that got out of hand," said Lawhorne. "The original idea was to take the cat and then release it."

The dean of students and his wife, who also live on campus, let the 7-year-old Burmese cat out of their house June 1, and the animal never came back, police said. During the first week of June, the couple put up fliers about their missing pet and notified the animal shelter.

Lawhorne said school officials told police in August that some of their students may have been involved in the cat's disappearance.

"We have treated it as a very serious matter from the beginning," said Hershey. He said that officials at the school, which was established in 1839, gathered students and told them what had happened.