He will be able to find shards of glass. There's the sound of countless windows smashing while he looks in the school, but nothing actually seems to be broken. Still, it's possible to find some pieces outside.

The blood appears normal, though it's worth noting the microscope wouldn't be powerful enough to look for things like nanobots, viruses, that sort of extremely small thing. Still, the blood itself it visible and doesn't look any more unusual than it would be for any of the characters (so any abnormalities related to their canons may show up if applicable).