A Plymouth Township man was charged this morning with beating, strangling and sexually assaulting the 14-year-old daughter of his girlfriend, then concealing her body in a plastic tub outside the home of a relative.

Ebony Nicole Dorsey, of Ambler, was strangled with her pajama bottoms at about 5:30 a.m. Friday by Mark O'Donnell, 48, of the 1900 block of Sandy Ridge Road in Plymouth Township, Montgomery County prosecutors alleged.

According to the dead girl's mother, the attack came after O'Donnell, who is married, had spent the night smoking crack cocaine in her Ambler home.

O'Donnell later disposed of the body outside a nephew's home on the 1300 block of Union Meeting Road in Blue Bell, Whitpain Township, authorities said.

Before her death, the teen had spent the night in O'Donnell's apartment, babysitting his 4-year-old daughter while O'Donnell's wife was out of town, an affidavit of probable cause said.

O'Donnell was charged with first-, second- and third-degree murder; involuntary deviate sexual intercourse, indecent assault, tampering with evidence and abuse of a corpse.

He was arraigned on the charges this afternoon before Magisterial District Judge Francis J. Bernhardt, and told reporters that he attacked the teenager because, "I caught her molesting my daughter."

In brief comments as he was led out of the court room, O'Donnell also said he was not high on cocaine at the time of the murder.

In his remarks, he also said, "I don't remember doing it."

O'Donnell is being held without bail.

The body of the Wissahickon High School freshman was found yesterday afternoon in a large, blue plastic tub that was concealed by leaves at the Blue Bell home.

She last had been seen Thursday night, when O'Donnell picked Dorsey up at her mother's house to baby-sit his 4-year-old daughter, Kyra, said Risa Vetri Ferman, Montgomery County first assistant district attorney.

O'Donnell then returned to the home of the girl's mother, Danielle Cattie, where he spent Thursday night. Cattie told police that O'Donnell ingested "a significant amount of crack cocaine" overnight, and was "wired" when he left for his apartment early Friday morning, the affidavit said.

There, O'Donnell found Dorsey in the process of changing Kyra's pull-up diaper on a sofa. He then yelled at the teen for changing his daughter in the middle of the night, and began slapping and punching Dorsey.

The assault continued into the daughter's bedroom, where the little girl witnessed at least part of the assault.

"(T)he next thing (O'Donnell) realized is that he had Ebony's pants wrapped around her neck," the affidavit said. "O'Donnell said he choked Ebony until his daughter, Kyra, said, 'Daddy.' O'Donnell realized at that point that Ebony was no longer breathing."

An autopsy determined that the teen died of blunt force trauma and asphyxiation. It also found anal tearing and bruising "consistent with penetration by a foreign object and sexual assault," the affidavit said.

The brutal tale then turned even more bizarre, authorities said.

O'Donnell told police that he emptied clothing from a plastic tub in his room, put the body in it and loaded it into the trunk of his Toyota. He then headed to the home of his nephew in Blue Bell, left the body in the tub at the side of the home, and departed.

He later returned and, without telling the nephew what he had done, covered the body with leaves.

More than 75 police officers and firefighters had been searching for Dorsey on Sunday. At the same time, authorities announced they were seeking O'Donnell for a second interview, following a brief discussion with him on Saturday morning. Investigators found him last night at the home of relatives' in Lower Gwynedd Township.

The relatives, apparently not knowing O'Donnell was there, had summoned summoned police after seeing signs that an intruder had entered the residence, Ferman said.

The discovery of the body in Blue Bell drew friends and family, who gathered across from the property, sobbing as firefighters hung a green tarp that blocked the tub from view.

At Dorsey's home in Ambler last night, a stream of friends and relatives passed through to offer condolences. Family members said they were too distraught to be interviewed; those gathered had concluded from information passed on to them by investigators that the body was Dorsey's.

"I just want everyone to know what a good girl she was," said family friend Tanitra Thompson. "She was an honor-roll student and loved by everyone. We will miss her, and she will always be in our hearts."

Dorsey had not been reported missing by her mother until Friday evening, despite her absence from school that day. Police said Cattie did not know whether her daughter had returned home in the interim.

Police said the last call made to the girl's cell phone was from her father, Evan Dorsey, at 7 a.m. Friday. He called his daughter every day at that time, Smith said.

Contact staff writer Kathleen Brady Shea at 610-701-7625 or kbrady@phillynews.com.