My 4 year old told me something happened at school

So, he told me that this older kid named we will call him “JJ” climbed under the bathroom stalls and touched his penis and his butt. And my son is in preschool and this older class is down the hall. They said they never combine the older and younger kids. I addressed this with the principle and his teacher. They both said he never said anything to them and his teacher told me she is 100% sure this never happened. They haven’t questioned the kid. My son says “JJ” is always mad and that he doesn’t like him. He also said that this JJ points his first finger and middle finger to his eyes and points at my son like he’s watching him. Preschool is only 3 hours a day, 4x a week. The ladies said I should take him to a child psychologist because maybe he is remembering something from another time. I called CPS to report it and they said they can’t take a report on another kid. That I would have to file a police report. This kid is 10 years old. I’m leaning on filing a police report. In the meantime I haven’t let my son go back to school. What would you do?