I’m not sure if Purdue is a “gun free” zone officially. It wasn’t when I was there.
I am not sure if it was when I was there (1967-1971). There were no firearms allowed in dorm rooms or on campus, but there were target rifles available for rent in the firing range on the west-center side of the campus. I also had some cherry-bombs with a wrist-rocket slingshot. Mad a lot of noise at 3:00am on a weekend. BTW, that was illegal to have, too.
I took many a class in the electrical building. It was on old (even when I was there), square brick building on the east-center side of campus.