New York police say they have subpoenaed Twitter to try to identify someone who threatened a Broadway theatre.
The New York Police Department is concerned about tweets that warned people would be killed at boxer Mike Tyson's one-man show.
One tweet referenced the shootings last month in Colorado that left 12 dead in a movie theatre.
NYPD spokesman Paul Browne said Twitter initially refused to disclose the source of the posts.
But he said the social media site had since turned over information in response to a subpoena, but he provided no further details.
A Twitter spokeswoman declined to comment.
Police recently beefed up security at the Long Acre Theater in midtown Manhattan as a precaution.