Police are investigating an apparent Occupy Wall St. protester’s online threat to kill cops.

Someone with the Twitter handle “smackema1” tweeted this message at 11:39 p.m. Saturday, following a clash at Zuccotti Park.: “we wont make a difference if we dont kill a cop or 2.”

The tweet was directed to a page on Ustream showing live footage of the protests.

The writer was had tweeted several comments about the protests Saturday night.

The NYPD is seeking a subpoena to find out who’s behind the Twitter account, according to Paul Browne, the department’s top spokesman.

Protesters attempted to stay overnight in the park Saturday, after their encampment was booted out Nov. 15.

“We had planned on being there for 24 hours,” said protester Aaron Black, 38, of Williamsburg, Brooklyn. “They were using their clubs and beating the crap out of people.”