Another Home Invasion Thwarted by Armed Homeowner

Here is a story from Austin, Texas about a homeowner that shoots and kills two teenagers who had broken into his home and who pointed a gun at him. There plenty of these stories and one hopes that word will get around to the potential criminals that home invasions are unsafe for the invaders (as well as the homeowners). However, this is what struck me in the story:

He said officials obtained a search warrant to collect evidence from the Chestnut Street residence, which is standard procedure, and that officials took four guns from the home.

It is perfectly appropriate and normal for the police to investigate a shooting even if it first appears an obvious case of self-defense. I have no quarrel with that. But it seems wrong to me for the police to take away the means of self-defense in case the little thugs' friend want to come around for a little revenge.