A former St. Paul Public Schools custodian peeked over and under a bathroom stall and smiled at a student in February, the latest in several alleged transgressions with young boys that date back to 2003, according to charges filed Thursday.

Walter J. Happel, 62, of Newport, was charged in Ramsey County District Court with one count of surreptitious interference with privacy.

The complaint shows that Happel kept working for the school district even though school officials knew about alleged misconduct with children for years. He allegedly shook his penis at a boy in a school restroom in 2011, but school officials did not report it after being notified of the incident by the boy’s mother. Nor did school officials return a follow-up phone call from the mother, the complaint said.

The boy’s mother first reported the 2011 incident to police when her son grew uneasy about going to school; the complaint did not indicate whether school officials later reported it as well.

Julie Schultz Brown, the district’s director of communications, marketing and development, said Thursday that she could not address what occurred in 2011, and did not know why it was not immediately reported to police by school officials.

“We are cooperating fully with the police,” she said. “We feel like we followed all the correct procedures in this situation. It’s the most difficult situation a school district can deal with.”

Schultz Brown said Superintendent Valeria Silva would not be available to comment.

Sgt. Paul Paulos, a police spokesman, wouldn’t say whether police are looking into the school district, but said the case continues to be investigated.

Happel was charged Thursday for a Feb. 19, 2014, incident at Linwood Monroe Arts Plus School. According to the complaint: An 11-year-old male student told his teacher that Happel peeked at him under the bathroom stall.

Happel was placed on paid administrative leave at 1:30 p.m. on Feb. 20. He was escorted from the building that day and told not to report for work. But Happel returned that afternoon, appearing “visibly shaken and disoriented” as he removed items on a dolly, the charges said.

Authorities later learned that he kept a secret room in the building that contained Enzyte topical intensifying gel, Stimulean energy capsules and a bottle of testosterone.

The school reported the peeking to police Feb. 21.

Happel started at the district’s facilities department in 1984, where he worked among adults. In 2003, Happel started working at Roosevelt Elementary School. He worked at Linwood, a pre-K through eighth grade school, from May 2004 until he resigned Feb. 26.

Happel allegedly gave a Roosevelt student a digital camera in 2003 so the two could take each other’s photos. The boy told authorities that he would meet Happel in the bathroom, where the janitor gave him candy. The boy said Happel did not touch him or ask him to undress.

Police were unable to access images on the camera, and the district addressed the issue internally, reprimanding Happel and ordering him to stop distributing candy.

Happel allegedly swatted a boy’s buttocks in 2011, the same year he allegedly shook his penis at a student. Happel’s personnel file mentioned the swatting case, but “it does not appear to have ever been reported to the St. Paul Police Department,” the charges said.

In the penis shaking incident, Happel allegedly followed a boy into the bathroom regularly for a year. The boy was using a urinal in Nov. 2011 when Happel approached and used one next to him.

“It’s a big thing,” Happel said, allegedly referring to his own exposed penis.

The boy’s mother spoke to a woman at the school the next day and “the woman’s reaction was that the janitor has been there forever and wouldn’t hurt anyone,” the charges said. The assistant principal and a special education teacher were aware of the incident.

“Happel received a reprimand in 2012 for both of these incidents,” the complaint said. “He was directed to use staff restrooms …”

Two students came forward this month to report other allegations of misconduct by Happel at Linwood.

Regarding the Feb. 19 peeping incident, Happel told police that he was looking for a messy stall and happened upon a student and looked at the area near his feet. Happel said the 2011 shaking case was “just unbelievable.”

Happel has not been charged in the other cases. It’s unclear whether authorities are investigating school officials’ actions in the 2011 cases.

No other cases have been presented to the county attorney’s office for possible charges, said spokesman Dennis Gerhardstein, but “there’s an ongoing investigation into a number of these incidents.”

Staff writer Nicole Norfleet contributed to this report.

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