“I wonder if anyone observed Holmes moving all that ammunition into his apartment, or all that other stuff he accumulated over a fairly short period of time. “
This is not illegal, though. So why would observing it make a difference?
We’d all like to predict when a crime’s going to occur. It’s only good human nature to try to see a type, a pattern, a tipoff. . .
but the fact is, we can’t. That is what “crazy” means. It doesn’t make sense, and we don’t know who is going to do what, when
It's not illegal, but when someone no one in the building knew anything about is buying ammo by the thousands of rounds, that might raise some suspicion, if anyone had seen him moving large amounts. Not many apartment dwellers buy ammo in those quantities.
And I bet few if any had ever been inside his apartment. Many people would have become very suspicious if they'd had knowledge of the sort of items Holmes was acquiring, all legally. But, of course, no one knew.