[GoLightly]

it's a million times more likely to be the work of someone with a specific grudge against Yale, or at least against a specific person at Yale. A Unabomber-style mailbomber out to get a professor, and the bomb went off in the mailroom somehow?

In that case, it's a good thing it was law school. If it had been a science major it would have gone off in the wrong place. You'd think a lawyer wannabe would target the prof or the school by suing them.

there doesn't seem to be a lot of hard physical damage

I'd call blowing out part of the floor pretty much hard physical dammage.

[El Gato]

In that case, it's a good thing it was law school. If it had been a science major

Some law students were science or engineering majors when undergrads, a few may have even worked in those areas before going to law school. OTOH, my daughter and her husband were both history types as undergrads, several thousand miles and a few years apart.