I really, really wish there was a stronger way these nutcases could be held accountable for threats posted on social media...
In the UK you can be charged criminally for shit like this. Not sure about the US. I don't know why you wouldn't be able to. If someone ever sent me a threat to my well being on twitter, my first call would be to local police and then I'd escalate from there. This behavior should not and cannot be tolerated in any form.