New charges of sexual misconduct filed Tuesday against a former St. Paul school custodian allege improper behavior with additional students in recent years and the repeated abuse of young family members decades ago.

Walter J. Happel, 62, resigned from his job at Linwood Monroe Arts Plus school on Feb. 26, as authorities began a criminal investigation into his behavior. In March, Happel was charged with peeking at an 11-year-old boy in a bathroom stall at Linwood Monroe. That prompted other abuse victims from the school and Happel's past to contact police, according to the seven new criminal complaints filed in Ramsey County District Court.

"On behalf of our community, I want to thank all of the victims for courageously coming forward to police about the defendant's sexual abuse," Ramsey County Attorney John Choi wrote. "He has preyed on the innocence of children for over 30 years, and I am relieved that we can seek to hold him accountable for these crimes and get him away from our children."

Five of the new cases involve Linwood Monroe students. Two of those students had reported Happel's behavior at the time it occurred, one in 2011 and another in 2012. But school staff members failed to alert police to the two cases, according to the complaints.

Also among those who contacted police was Happel's son, who said his father had abused him, other family members and friends.

Happel will not be charged in his son's abuse, said county attorney spokesman Dennis Gerhardstein, but two of the new cases involve a family friend and a relative of Happel's who were abused about 30 years ago.

Those alleged victims, men who are now in their late 30s and mid-40s, told police that Happel started abusing them when they were 8, too young and scared to report the years of gropings, naked photography and rape.

Allegations that Happel had sexually abused a family member were known to St. Paul police as far back as 1991, and in 2003 Happel was reprimanded by his supervisor at St. Paul schools for giving candy to children at Roosevelt Elementary School and for ignoring orders to stop the behavior. But he continued to work alongside children, many of whom told authorities that he regularly followed them into school bathrooms and looked at their penises.

Schools Superintendent Valeria Silva has declined to discuss the Happel case since the original charge was filed, including his 30-year career with the district and staff's handling of the 2011 case where he allegedly followed a boy into the restroom and showed the student his penis, and the 2012 case where he allegedly slapped a student's butt.

In a written statement issued Tuesday, district spokeswoman Toya Stewart Downey said news of the new charges came late in the day Tuesday, and that timing and "a high-energy" school board meeting made it impossible for someone to review them and respond.

Happel was charged Tuesday with one count of first-degree criminal sexual conduct, three counts of second-degree criminal sexual conduct, one count of fourth-degree criminal sexual conduct, one count of fifth-degree criminal sexual conduct and four counts of surreptitious interference with privacy. Happel was charged in March with surreptitious interference with privacy for the Feb. 19 incident at Linwood Monroe, which the school reported to police.

According to the first-degree criminal sexual conduct charge: Happel allegedly abused his son's friend, now grown, when he was between age 7 and 9. The boy, about 9, went to the school where Happel worked, and Happel told him to shower.

"Happel got close and kept hitting [the boy] with his penis," the complaint said. "Happel laughed about it and said, 'Oh, I'm sorry. I'm sorry.' "

The boy later stayed over at the Happel house in St. Paul. Happel woke the boy from his sleep, fondled him, photographed him and then raped him, the complaint said.

The student from the 2012 slapping incident told authorities that sometime in late 2010 when he was in sixth grade at Linwood Monroe, Happel leaned his erect penis into the boy's buttocks.

Authorities also learned that Happel kept a secret room at Linwood Monroe that contained a topical intensifying gel, energy capsules and a bottle of testosterone.

Happel was being held in the Ramsey County jail Tuesday on $100,000 bail, pending a Wednesday court appearance.

Staff writer Anthony Lonetree contributed to this report. Chao Xiong • 612-270-4708 Twitter: @ChaoStrib