Dear Delta —
As Eric said, tell the Bishop, in writing, and via an appointment if possible, and get additional witnesses. There is a chance that your bishop may already know, in which case he won't act unless there is sufficient pressure to do so.
This is the sad state of affairs these days but it is up to the laity to call these evil doings out if we ever want to see our Church purified. All through history saints spoke up and even confronted the hierarchy when bad actors despoiled Christ's Church.
Be brave and shine the light, but be armed with facts and other witnesses to be taken seriously.