COLUMBUS, Ind. -- A man arrested in connection with last week's slaying of a Columbus girl stabbed her after she awoke while he was trying to steal car keys from an apartment, police said.

Police said Demetrick D. Shepherd, 20, admitted on Sunday that he stabbed 14-year-old Chelsea Porter early Friday in an apartment where one of her friends lives.

Police said Shepherd is acquainted with the son of a woman who lives at the apartment. According to a probable cause affidavit, Shepherd broke into the home -- where Porter was staying to help her friend's family with a birthday party -- with the intention of stealing keys to the woman's car.

Porter, who was sleeping on a couch, woke up, and Shepherd stabbed her numerous times with a knife he took from the apartment's kitchen, police said.

"We do believe he was meaning to kill Chelsea," Columbus Police Chief William Martin said at a news conference Monday afternoon.

Police said a neighbor called 911 to report the stabbing at about 3:50 a.m. Friday. Porter was taken to a hospital, where she was pronounced dead. She had been stabbed repeatedly in the neck, police said.

Investigators questioned Shepherd on Friday and arrested him on Sunday after he confessed, police said. Shepherd told investigators where to find the knife, authorities said.

Porter, who attended Central Middle School, was developmentally disabled and had speech and hearing problems, 6News' Jack Rinehart reported.

In a statement released to the news media Monday, Porter's family said she "was an important part of our lives."

"The untimely loss of her is one of the greatest pains any family can imagine," the statement said. "She loved children and enjoyed going to church. We will miss her greatly in the days, months and years to come, but she will forever be in our hearts and in our memories."

Shepherd, whose home is close to the apartment, was being held Monday in the Bartholomew County Jail on a preliminary charge of murder. Police said the county's prosecutor was reviewing the case and that Shepherd could face other charges.