The suspect doesn't attend Yale but could get into a secure facility? So much for building security.
I've been to Yale's medical complex many times, including the buildings on Cedar and Amistad. It's like any other building with keycard access. You can't get in without a keycard, but if someone is entering the building, you can follow them in through the temporarily open door. You could also wait outside until you see someone leaving the building, and then do the same. Students are told not to hold the doors open for others, but you know how it is. It's not very polite to slam the door or force it to close quickly if you can see someone coming, and I observed that most people around Yale hold doors open for others if they see someone approaching - especially if they look like a student (as opposed to a person who looks kind of scary) and it's during the day.