PORTLAND, Ore. (KOIN) — James Mattson, who pled guilty to 137 counts of voyeurism, was sentenced to 10 years in prison Friday.

Mattson is a former janitor for the Vancouver School District and pleaded guilty to making recordings of students and staff members while they undressed in school bathrooms.

The secret recordings date as far back as 2013.

Over a dozen of the 55 victims who were identified so far testified at the trial.