PROVO — In retrospect, the boy’s mother thinks today, she should have suspected that something was wrong when her 10-year-old son came home from a field trip to a bowling alley and immediately wanted to take a bath, saying he was sore and didn’t feel well.

It wasn’t until three years later, after she’d slowly watched her happy and kind little boy morph into a stranger — one who physically harmed himself, who stole cigarettes and alcohol, who sent crude text messages about his female peers — that her son told his mother what had happened to him that day at the bowling alley. His school principal, the boy said, took him into the bathroom there and sexually assaulted him.

"It did feel good to finally say something about what happened, but it was also really scary at the time because I didn't know what people were going to think of me," said the now-17-year-old boy, who asked to remain unnamed, sitting in his family's home in Provo on Wednesday. "I didn't realize how severe my trauma was until (I told my mother) that day."

The principal was Charles Edwards Weber, convicted in 2013 of assaulting a different 15-year-old boy. Prosecutors in that case have said they were aware of more victims, including a man Weber taught in the 1970s.

Now, the boy who says he was assaulted in a bowling alley bathroom and his mother are suing Weber and Soldier Hollow Charter School in Heber City, saying the school should have done more to investigate earlier reports of misconduct that hinted the principal might sexually abuse students.

The teenager says he hopes the lawsuit, filed Monday, sends a message to other survivors of sexual assault: "Don't be afraid to talk, because if you don't talk it doesn't help anyone."

There's also a practical financial component to the lawsuit, which seeks damages of at least $50,000, the family says. Since fifth grade, the boy has gone through extensive and ongoing treatment for depression, anxiety, schizoaffective disorder, and other mental health-related afflictions that the family says was brought on by the trauma of the alleged assault. He's currently on four medications, his mother said, one of which alone costs the family $1,200 per month.

"Imagine being quadriplegic and needing help 24 hours a day, 24-7. It's kind of the same situation with my mental health," the teenager said. "I'm definitely going to need therapy for the rest of my life, and (medication) for the rest of my life."

A police report was filed after the boy came forward with the assault allegations, but authorities did not pursue the case because Weber had already pleaded guilty to sexual misconduct with the 15-year-old and was headed to prison, according to the boy's attorney, Daniel Ellis.

Attorneys for the teen argue that sexual harassment and abuse was foreseeable based on past complaints from students, parents and teachers. The lawsuit claims that the board failed to fully investigate or take action to protect students, such as monitoring or limiting Weber's interactions with students, warning parents of the prior reports or training teachers to prevent misconduct.

The Soldier Hollow board of directors said in a statement that the board is "very concerned about these allegations and takes them seriously."

The board added that it has turned all matters related to Weber over to the Utah Attorney General’s Office since firing the former principal in 2012, and said it could not comment further as the case is in litigation.

Soldier Hollow administrators had previously received several reports of Weber acting in sexual and inappropriate ways with his students, including from a mother who told the school's governing board in 2007 that "something weird was going on between Principal Weber and her son," according to the lawsuit. In 2009, several parents, employees and teachers complained to the board that Weber routinely used the student restroom on campus and removed all of the privacy panels in the restroom.

"The only conceivable purpose of this action was so that Weber could look at students’ genitals," the suit states. Two other reports from parents that year alleged Weber had been "slapping the butts" of girls and boys at the school and would routinely bring students into his office alone and close the door.

When the boy was in third grade, he said in an interview, the principal would take him into his office, where he would sit the boy on his lap and rub his leg.

"I think as young kids, especially boys, when somebody you trust grooms you like that, I think inside your soul you know it’s wrong, but what do you do?" the teenager's mother said through tears Wednesday. "Charles Weber's masking of who he truly was was incredible."

Weber was arrested in 2012 after he "admitted to sexually abusing several young boys over the past 35 years," according to an FBI affidavit from the time. He was sentenced to two consecutive terms of five years to life in prison for two counts of forcible sodomy, a first-degree felony.

"It helps knowing that it's not going to happen to anybody else, but it's not something that eases me," the teenager said. "Even if he is in jail, it still happened to me. No matter where he is in life, it happened to me."

Contributing: Annie Knox