PARKLAND, Wash. -- A 23-year-old man is accused of killing a baby girl who was found dead in her crib in her mother's apartment on Friday.

The man, who is the girl's mother's boyfriend, was arrested Tuesday by Pierce County Sheriff's deputies.

He is being held at the Pierce County Jail on $50,000 bail, and is being investigated for second-degree murder of the 1-year-old girl.

Investigators said he was arrested after his story of how the girl was injured kept changing.

On Friday, deputies were called to bottom floor unit at the apartment complex after the mother came home from work to find her infant daughter unconscious in her crib.

Hours before deputies arrived, neighbor Samantha Starkovich heard a loud noise coming from the apartment above. Then silence.

Starkovich remembers that, "at 12 or one o'clock, we heard some loud bangs with some fireworks. He went to the laundry room to do some laundry and he never came back."

Deputies said the 23-year-old man first told them the baby fell off the couch and then he put her to bed and she fell asleep.

But the autopsy came out, and the boyfriend changed his story, deputies said.

"The injuries are not consistent with falling off the couch. There are multiple skull fractures and severe trauma to the torso, nothing you would get falling off the couch. We believe the baby was assaulted," said Ed Troyer of the Pierce County Sheriff's Office.

Neighbors said the boyfriend's story sounded fishy.

"There is no way a baby could die falling off a couch, unless it's 12 feet tall. No way," said Jennifer Garcia.

"That is kind of odd, a healthy baby kind of dying," said Julie Waters.

The suspect is expected to have a bail hearing in Tacoma Wednesday afternoon.