Believe him or her. People do not lie about sexual assault. When your friend is hurting, it is always better to believe than accuse.
Listen in a supportive way. Keep calm. Offer options; don't make decisions for them - they need to regain a sense of control.
Let them know this was not their fault. No manner of dress, no inappropriate behavior, no amount of alcohol, no wild party, is an invitation for rape. Nor can most victims protect themselves from an intended rape.
They are the victim of a violent crime; they have survived and may need medical attention. Ask if they want you to accompany them to the hospital, or police.
Respect their privacy and confidentiality; do not tell anyone without their consent.
Ask them how you can help. Do they need a safe place to stay? Offer to contact resources for them. Unless they clearly need immediate medical attention and cannot speak for themselves, only do for them what they ask you to do.
Seek advice and counseling for yourself if you need it
Do not pursue the attacker! Charges of assault and battery in attempts at revenge have seriously compromised legally charging the rapist. Focus on taking care of your friend, and yourself, first.
Call 911 on campus for emergency police.
Kishwaukee Hospital is prepared to collect evidence kits in rape cases.
The campus call boxes will connect you to the police when you pick up the phone.