People do not typically murder their families or loved ones just to murder them like a "usual" killer does. Its usually a crime of passion or emotion for which they will still commit if a gun is not around. Of course guns make it easier, but for anyone that is intrested in killing, that wont stop them. This sniper character in the news now may not have been been doing this, but I bet the guy that you stated killed his wife would have still done so without a gun.
As far as accidents around the home with guns. With kids, it is usually poor parentiing. Almost all of my familiy members had guns in the house including my old man. At 12 he took me hunting. He taught me how to properly shot and most importantly respect a firearm. As many times as I had friends over, I never once pulled his guns out to show off as many of the kids do right b4 one of them ends up dead.
Now on to the parents that dont want to teach their kids about weapons in the house. Plain and simple, poor parenting. If they do not want their kids to learn abut them, they need to have said weapons locked up at ALL times.
As always, guns dont kill ppl, stupid and uneducated muthaluvas with guns kill people.(accidently anyway)