Yes and No
"At the current time we're taking the firearms for safe keeping as evidence until we can further investigate this," says Deputy Chief Lindmark.
Securing the weapons until the owner returns... they have to since the burglars, and now the entire neighborhood & everyone who reads the paper knows the weapons are there and that the owner is not. The weapons could be easily stolen, thanks to the police & media announcing it to everyone.
However... "as evidence until we can further investigate this," is wrong. If there's no law broken or there's no suspicion of a crime committed by the homeowner, then the weapons are not evidence.
There should be no serial numbers run, no ballistics checks, nothing but securing and holding the weapons (due to the house being condemned and unsecure) until the homeowner returns.
If something is found during a proper investigation (the burglary) that is in itself illegal (ie a bag of pot) then they have the right to seize it and start a separate investigation, but they can't start an investigation on nothing.
Are they running the serial numbers on every TV & appliance in the home to see if they are stolen? They can't base an investigation on the amount of legal items in the home, who would decide where to draw the line on how many is too many?
All the homeowner should have to worry about is dealing with his now condemned house and getting professional help on his "hording" problem (not just the weapons, but the whole house issue).
edit: If there are state laws where he lives dealing with weapons secured in the home, ie must be in a gun safe or trigger locked, then my opinion stated above would be somewhat different. I know some states/cities have laws to this effect.