Aggressive behavior and Daycare

Hey everyone, I am needing a little reassurance about feeling like I am doing the right thing with my daughter. My daughter is in daycare 3-4 days per week and moved to a new classroom in August which including having some new kids added to her class. Well they now have a non verbal child who is extremely aggressive. As far as I know it has never involved my daughter as far as being the one he is physical with. However my best friend (her daughter is also in this classroom) witnessed around a month ago him shoving another little girl in the class down and start repeatedly kicking her. Well today I was walking the hall to pick her up and I heard the teachers discussing how extremely aggressive this child still is being. I asked one of her teachers and she said it is to the teachers not the children. But then we get home and my very verbal daughter says "So and so hits this girl all of the time." With no prompting just asking how her day was. I guess I'm just wondering if I should bring it up to the daycare supervisor or wait and see if it starts affecting my child or my best friends, who I treat as my second daughter. Yes I understand that they are at the age of testing limits and not understanding their emotions or how to express them correctly. But I also don't want my daughter where she isn't in a safe environment. Side note: I am diagnosed with severe postpartum anxiety and depression. So I tend to overthink and over worry things. But opinions and reassurance are more than welcome.