Amber Jackson couldn't possibly have known.

She couldn't have known that when she was dancing with Freddie Cleveland at her senior prom three years ago, she had her arms wrapped around her killer.

"She was butchered, she was slaughtered," Upper Darby Police Superintendent Michael Chitwood Sr. said of Jackson's death, a homicide so brutal that it stunned hardened police veterans.

Yesterday, Cleveland was under police guard at the Hospital of the University of Pennsylvania, charged with killing the 20-year-old state-police dispatcher in her parents' bathroom Tuesday night.

Cleveland, 22, is awaiting a bedside arraignment on murder and assault charges for allegedly stabbing Jackson after she tried to end their relationship, which began when she was a cosmetology student at Mercy Vocational High School.

Chitwood said that he was "hopeful" that Cleveland - whose stab wounds were self-inflicted, police believe - would be arraigned today.

Chitwood said that Jackson had been stabbed so many times that crime-scene investigators "stopped counting at 30."

"Significant stab wounds about her head, face, neck," he said. "And when I say significant, I mean really, really bad.

"You could see the anger that he had toward her - the hatred, probably," he added. "To do that to another human being, I don't think there's a word to describe it."

Jackson, a police-radio dispatcher in Norristown, graduated from Mercy Vocational in 2006 and was expected to graduate shortly from Delaware County Community College with an associate's degree in business administration.

"She was a good student for us," Sister Susan Walsh, the high school's principal, said yesterday. "She was a good kid. Really conscientious, focused, polite, sweet - very much a lady around her classmates."

Jackson and Cleveland, a sanitation worker for Lansdowne Borough who attended Overbrook High School, had lived together in the Drexelbrook apartments. But when she moved out, he couldn't let her go, police said.

"She felt the relationship wasn't what she wanted it to be and wanted to come back home," said Jackson's uncle, Lt. Shelton Sneed, a state-police station commander in Avondale. He said that her older co-workers "looked at her as a daughter."

Jackson was talking with a friend on her cell phone Tuesday night when Cleveland confronted her outside her parents' Drexel Hill home. Chitwood said that the friend on the other line heard Cleveland say, "Please tell me it's not over. Just come out and hug me. Just one more hug," before the phone cut out.

Jackson locked the door and told her 13-year-old sister to hide, and to call police and their father. She did, but neither arrived in time. Cleveland broke through the plate-glass front door and grabbed a kitchen knife, police said.

"The 13-year-old hears noises, doors slamming," Chitwood said of Jackson's sister, who hid in a closet. "She heard her sister, Amber, telling Frederick Cleveland, 'Please don't hurt my sister!' "

" 'Daddy, daddy, come home! Amber's being hurt!' " the younger sister said into the phone, according to the police report.

Police found Jackson in a pool of blood in the upstairs bathroom. Two of her fingers were partially severed, in what appeared to be defensive wounds. She was pronounced dead at the scene.

Downstairs, Cleveland was minutes away from death. He had lost an enormous amount of blood from stab wounds, and police are investigating the possibility that he tried to take his own life.

"We believe they were self-inflicted, yes," Chitwood said.

He declined to say whether Cleveland had given police a statement about his involvement in the crime.

Staff writer Michael Hinkelman contributed to this report.