How could this happen in the safest city in America?

Something with this story just doesn't seem to add up. Is this just a horrible tragedy where 31 year old David Park just walked into the wrong house? An anti gun person would say this is one reason we don't need guns. Too much potential for accidents. A pro gun advocate would say the Amherst homeowner was well within his rights to shoot the man. To me, it just seems like there is more going on here than the Amherst police are telling us. Shouldn't the homeowner have realized that the victim didn't pose a threat? Or was there so much confusion that the victim never realized he was in the wrong house? Since when do guys go to baby showers, much less get drunk at one? Was the neighbor's door left unlocked at 1AM? Hopefully, more information will come out regarding this story.
Albany teacher fatally shot in Amherst : Northern Suburbs : The Buffalo News