Somone is threatening to rape and kill online what can I do?

[Mia]

Someone on twitter keeps saying they are going to rape and kill me. I blocked this person but people are telling he is saying these he is going to do these horrible things to me. I don't know this person but it's scary and I don't want to @ me name an say these things. What can I do to stop this? It scary and disgusting and I want this person to stop.
Honestly I'm scared if this person find out my address he will really do these things, he is crazy and this all started because this person defends criminals like himself and I retweeted my friends tweet to him and I did not even talk to him and he started following me saying he was going to rape and kill me
I did tell him I was reporting him to twitter he said he will just make another account to harass and threaten me

[ChA 1988]

Better report it to the police.

[Chris]

file a police report if you seriously feel threatened. they can file a request for the users ip address and other registered info, track them down and arrest them.

[Charles]

Make a police report, Now.

[John H]

Report to police. That's simple enough.