Valley Park, Mo. ? A 6-year-old girl vanished from a suburban St. Louis home Friday and was killed by a man who had stayed there overnight, police said.

Cassandra Williamson was reported missing Friday morning from her father’s home. Police said the suspect, a 24-year-old local transient who had slept on the couch, later told them the girl’s body was at an abandoned glass factory a few blocks away.

A group of search volunteers who had been going door-to-door arrived about the same time as investigators at the factory, where the girl’s body was found.

Late Friday night, Cassandra’s parents went to the crime scene and identified the body, said James McCrady, a St. Louis County Medical Examiner’s Office investigator. The parents, hugging and crying, later were chauffered away behind the coroner’s van carrying their daughter’s body.

St. Louis County Police Chief Ron Battelle said Johnny Johnson was arrested but charges had not yet been filed. Johnson spent the night at a home shared by Cassandra’s father, Ernie Williamson, and a roommate, the father said.

Ernie Williamson and Cassandra’s mother, Angela Williamson, had separated but still spent some nights together at a neighbor’s home, where Ernie Williamson had been staying for about a week.

Thursday night, the entire family stayed at the home Ernie and Angela Williamson and their four children.

Police described Johnson as a local transient who sometimes slept in the factory. Ernie Williamson said he had only known Johnson a few days and that his roommate and Johnson were up late drinking the night before. He said Johnson was sleeping on the couch Friday morning.

Authorities said Cassandra was in the kitchen around 7:30 a.m. with her father. Williamson said he was about to pour his daughter a bowl of cereal and left the room briefly to go the bathroom. When he returned, the girl, barefoot and dressed in a white nightgown, had disappeared.

The father said he also noticed that Johnson was gone. About a half-hour later, Williamson said, Johnson returned to the house, wet and muddy, and said he had been swimming in the nearby river. Police began questioning him soon after he returned.

Before the body was found, Cassandra’s mother, Angela, said, “She never walks off without telling me she’s going somewhere. She doesn’t even go to her friend’s house without telling me she was going. I just want my baby.”

As word of the disappearance spread, volunteers began joining in the search, which also included helicopters and bloodhounds. Many were looking around an area along the Meramec River, which runs through Valley Park in southwest St. Louis County.

Several cases of child abductions involving young girls have been in the news in recent weeks.

Cassandra, who would have been a first-grader in the fall, had been chosen as the kindergartner to represent a new generation and launch a handful of balloons as part of a Sept. 11 remembrance ceremony at school, said Valley Park School District spokeswoman Barbara Roux.

“She was thrilled. She just wanted to do it perfectly,” Roux said. “She kept asking, ‘Am I standing right?’ She just wanted it to be perfect, and she was perfect.”