Hello, police departments!
Perhaps the script for responding to a call from someone announcing that he's killed his wife and is holding hostages and/or planning to shoot at responding cops should include a new first step:
Call him back and ask if it's really him.
Really. Could save considerable trouble. If it's not him, you can give him a heads-up that you need to send someone around for a welfare check, and avoid misunderstandings. If it is him, well, letting him know that you received his call isn't exactly going to reveal any information he didn't have before.
Also, hello telephone companies!
Perhaps you should filter calling number ID, to disallow spoofing of any number that hasn't been registered as VOIP or sometimes-VOIP, or some other legitimate reason for being spoofed? That is, make sure that the person to whom the number is assigned has in some way announced his intention to use the number in nonstandard ways?
(Yeah, there are legitimate reasons for the owner of a landline number to be spoofing it over VOIP, e.g., from overseas. But I can't think of any legitimate reason for a third party to be spoofing a number without explicit prior authorization.)