WELLINGTON, Colo. -- Authorities in Larimer County said a 14-year-old girl was sexually assaulted early Sunday morning by a man who may have used a spare key to get inside her house.

The assault happened in the small town of Wellington and the girl had been home alone. She had told her mother that she was going to spend the night at a friend's house but changed her mind and went home instead.

"She just decided to come home and watch movies and mom didn't know," said the girl's grandmother.

She told investigators she awoke about 3 a.m., to find a bald man next to her bed and that he assaulted her while holding a pillow over her face. Later she called 911 and ran to a neighbor's house.

The girl was not able to provide a detailed description of her assailant, but investigators were following several leads and were interviewing two potential suspects. They were also processing forensic evidence collected at the crime scene.

The assault was reported in the 3700 block of Box Elder Court.

"Evidently he's watched my granddaughter get in (the house)," said the grandmother.

The family changed the door locks on their home Sunday.