Why?

The killer at Virginia Tech had “obliterated” the serial numbers on his weapons. This has returned to my thoughts over the past two weeks. Why would he do that? He certainly wasn't attempting to hide his identity and why should he care if the weapons were traced after he was dead, which apparently was the intended result.

I'm sure one can construct amazing conspiracy theories based on this loose-flapping factlet, but somehow I suspect it was simply because all the cool killers file off the serial numbers on their guns. sigh