The cryptic college campus killer

You are gathered around the latest victim with your partner. This has been the fourth one this month, and yet you are no closer to solving the mystery. The victim is a history student, apparently lead into one of the janitorial closets and killed. The method isn’t obvious and you are still waiting from a report from the morgue about any of the previous ones. Your partner notices something.

Look! There’s a small slip of paper in the victim’s hand!

Indeed there is. You take a closer look at it and discover it has a note on it. Maybe it is a crucial clue.

521b why how

It makes no sense. You can’t see any meaning to this note. You consult your partner about the previous victims, trying to find a pattern.

The first victim was a computer scientist.

The second victim was a mathematician.

The third victim was a chemist.

The fourth victim, this one, was a historian.

There’s no correlation, no motivation you can see that would connect them. You prepare to leave to mull over this information when you spot a note on the wall. Surely that wasn’t there before. You would have noticed it earlier. It says:

OWOLTSZWRXDVBYIZJHCQJUTXEPSHVFQEIXLVUOUCMHTJXZFFYJPKFXECLGYHXCYHMRRIDOTVVUPDIFANZHROQCB

This must be a clue! You take it from the wall and begin work on decrypting it.

What does the note say?

Hint 1:

Hint 2:

Hint 3: