If someone you know is raped or sexually assaulted, would you know how to help? In situations like these, feelings of trust and security may be diminished, and often the best way you can help is to provide support. Offer to stay with them; ask them if they feel safe, and make sure they know you believe them. Make sure that they know you are around to lend a compassionate ear, but also allow them to share at their own pace, and help them access local and university resources that may be helpful.
https://health.cornell.edu/resources/health-topics/assault-harassment