New York Police Department has used a subpoena to force Twitter to disclose information about the source of a tweet saying people were going to die at the Broadway theatre staging a one-man show by Mike Tyson.
The NYPD sought the subpoena after Twitter refused to co-operate in a probe of ominous posts that referenced the shooting deaths last month of 12 people at a showing of The Dark Knight Rises at a Colorado cinema, said NYPD spokesman Paul Browne.
Officers have now received new information from Twitter "that we're using as part of our ongoing investigation", the spokesman said.
Police said the tweets appeared to be aimed at the audience for Mike Tyson: Undisputed Truth, the solo show by the former heavyweight boxing champion, directed by Spike Lee at the Longacre Theatre in midtown Manhattan.
Police said one tweet read: "This s**** ain't no joke yo I'm serious people are gonna die just like in aurora."
Another from the same account warned: "I'm in Florida rite now, but it'll happen i promise I'm just finishing up my hit list."
Before complying with the subpoena, Twitter told the NYPD in an email: "We appreciate the timeliness and sensitivity of this matter, and have reviewed the reported Twitter account.
While we do invoke emergency disclosure procedures when it appears that a threat is present, specific and immediate, this does not appear to fall under those strict parameters as per our policies."
Mr Browne said the NYPD has beefed up security at Longacre as a precaution.