ST. LOUIS (AP) — A St. Louis teenager was charged with first-degree murder in the strangulation of Vashon High School's co-valedictorian and homecoming queen, leaving her family to lament what they call the cautionary tale of an abusive relationship.

Leonard Johnson, 17, was the sometime boyfriend of 18-year-old Sarah Billingsley-Walker. She was found dead the night of March 12. An autopsy determined she had been strangled.

Johnson was arrested and charged on March 14. He was jailed and did not yet have an attorney.

Relatives told the St. Louis Post-Dispatch that they had warned Billingsley-Walker to stay away from Johnson, who, they say, had shown signs of violence.

“I want Sarah's story to be told because if you are in an abusive relationship you shouldn't hide it from your parents because they are the ones that really love you,” her mother, Lavaughn Walker, said. “If you feel you can't talk to them, then go to your counselors at school. Don't think it's going to get better because it's not. If she would have listened to me, she'd be here today.'”

On March 12, Billingsley-Walker called her sister, Lavonda Walker, and said she was at a friend's house and that he was acting strangely and wouldn't let her leave.

Walker was filing a missing-person report with police when she got a call that Billingsley-Walker was dead. The friend turned out to be Johnson.

Relatives said that as fast as Billingsley-Walker was rising, Johnson was falling. The two dated for about a year. Her mother and stepfather didn't approve of the relationship. They recalled that he once kicked in the door of their home and accused Billingsley-Walker of cheating on him.

“I told her to leave him alone and that ‘He will pull you down,’” Lavaughn Walker said. “I told her some smiles are wolves' smiles.”

The family thought Billingsley-Walker had moved on. It had been about half a year since anyone heard her speak of him. That's why Lavonda Walker didn't think her sister was at Johnson's home when she got the call.

“If I would have known she was there, I would have called the police right away,” Lavonda Walker said.

Still, when Billingsley-Walker didn't answer her cell phone, her mother thought of Johnson and went to his family's home. He said he had spoken to Billingsley-Walker earlier in the day and was “kind of mad” about a new boyfriend. But Walker said he did not appear nervous and showed no signs of a struggle.

“He walked me to my car and gave me his phone number, telling me to call him if I heard from her,” Walker said.

Police have not explained the circumstances under which the body was found. Court documents said someone told police that Johnson admitted choking the victim.

Billingsley-Walker, one of Lavaughn Walker's five children, was in the National Honor Society and was a member of Vashon's dance team. She worked as an intern at the Urban League of Metropolitan St. Louis, doing paperwork for those seeking assistance with utilities.

She had already been accepted to four colleges and was leaning toward a major in political science and history at Philander Smith College in Little Rock, Ark., which offered her a full scholarship.

“She wanted to be a lawyer,” her mother said.

Neighbor Yvonne Petty, 51, said Billingsley-Walker was an inspiration to other young people.

“It's very seldom when you get a child in the community who is an ‘A’ student and valedictorian,” she said. “That's the type of life she lived.”

Vashon officials held an assembly March 13 to tell students of the murder. Lavaughn Walker said she plans to attend Vashon's graduation ceremony and display her daughter's diploma.

Information from: St. Louis Post-Dispatch,