...Mid-Morning Visitor...?

So when I say mid-morning visitor, what I really mean is early morning... as in 4 AM. Last night, my roommate and some of her friends fell asleep on the couch watching TV and she woke up this morning when she heard someone walking around the apartment. He walked over, looked at everyone who was asleep on the couch, picked up a set of keys off the coffee table, crouched down behind the couch, and then walked out. So she woke everyone up to take them home, and realized that he had picked up her keys off the table... So now this random person that no one knows has a key to her car AND to our apartment... Comforting thought, right?... Not so much... She was able to use a friend's car to take everyone home. So then she came in and woke me up to tell me what happened. Needless to say, she slept in my room with me. Except neither of us could go back to sleep. So as I said, a random man has the key to our apartment and Mataya's car... obviously not the safest situation in the world. So we called the University Parking Enforcement and asked them to boot her car so that if he tried, he wouldn't be able to drive away in it. Then, because it's Saturday, we had to call the emergency number for our management company and tell them what happened. She was understanding and called a locksmith to come change the lock and deadbolt on our door and make us all new keys. Unfortuately, I was home by myself during all of this and was scared out of my mind that he was in the apartment. I think I probably checked the closets and bathrooms about 17 times (Apparently once wasn't enough). Thankfully, the locksmith came within about 2 hours and was able to replace the locks. We have now decided that the door stays locked 24/7...