This scam is a type of extortion. It is an uncommon and unsophisticated scam that attempts to extort money from victims through fear. The usual format is an email claiming to be from an assasin hired to kill you but that you can stop your own murder by sending money to the killer.
Receiving a death threat like this can be frightening but there is no actual danger to the recipient. The scammer is only using it to try to extort money. As with most scam emails, it has been sent to many people and the scammer probably knows very little about you beyond your email address. You can read more about this type of scam here: Consumer Fraud Reporting
If you receive one of these emails you should report it to the FBI's Internet Crime Complaint Center.
If you receive any other sort of email threatening violence to you, especially if it contains any of your personally identifying information or you know the sender, please report it to your local police.
Samples of hitman scam emails:
LISTEN VERY CAREFULLY ,THIS IS THE ONLY WAY I CAN CONTACT
YOU, my TEAM HAS BEEN PAID TO ASSASINATE YOU, I HAVE EVERY REASON TO
CARRY OUT THE CONTRACT,BUT I DECIDED TO GIVE YOU A CHANCE AND SAVE YOUR FAMILY THIS PAIN,THIS YOUR ALTERNATIVE,I WISH TO HELP YOU UNLESS YOU
DONT WANT TO HELP YOUR SELF,I WILL SEND YOU ENOUGH EVIDENCE YOU NEED ON A VIDEO TAPE RECORD
TO NAIL MY EMPLOYER DOWN WITH THE LAW.
BEFORE THAT YOUR REQUIRED TO MAKE AVAILABLE THE SUM OF $100,000. USD
AFTER WHICH I WILL DIRECT YOU ON WHAT TO DO NEXT TO SAVE YOUR SELF AND
YOUR FAMILY FROM THIS PAIN THAT WOULD HAVE BEFALLED YOU FROM MY
EMPLOYER,THE MONEY WILL BE USED TO SETTLE THE TEAM MEN INVOLVED TO GO
BACK TO THERE DESTINATIONS AND YOU BETTER KEEP THIS INFORMATION TO
YOUR SELF BECAUSE YOU DONT KNOW WHO IS WHO WHERE YOU ARE NOW,IF HE
FINDS OUT I HAVE BETRAYED HIM TRYING TO HELP YOU,YOU WILL HAVE YOUR
SELF TO BLAME, I HAVE ORDERED MY MEN TO SATY AWAY FROM YOU.
DO WE HAVE A DEAL OR NOT ?
NOTE: YOU HAVE TWO OPTIONS HERE, (1)YOU HAVE TO GET HIM ARRESTED WITH
THE INFORMATION I WILL GIVE YOU AFTER THE PAYMENT OR ( 2)YOU HAVE HIM
KILLED TO SAVE YOUR SELF.
I WILL VISIT YOUR HOUSE AGAIN BUT NOT NOW,MY BOYS EYES ARE ON YOU SO
GET BACK TO ME AS SOON AS POSSIBLE
This is the only way I could contact you for now,I want you to be very careful about this and keep this secret with you until I make out space for us to see. You have no need of knowing who I am or where I am from.I know this may sound very surprising to you but it's the situation. the problem is, if i do'nt KILL YOU somebody else will. i have been paid some ransom in advance to terminate you with some reasons listed to me by my employer.It's someone I believe you call a friend, Do not contact the police or try to send a copy of this to them,because if you do, I will know,and might be pushed to do what I have been paid to do, this is the 1st time I turn out to be a betrayer in my job. I took pity on you,that is why I have made up my mind to help you if you are willing to help yourself.