Cops chased a 29-year-old man right into the Harlem River after he threatened to kill an officer early Sunday, police sources said.

Anthony Casiano, 29, first started yelling, “Don’t do that!” and, “I’m going to do video!” as police officers arrested a man on drug charges at 175th Street and Audubon Avenue in Washington Heights around 1:50 a.m., sources said.

Casiano then spewed out a death threat, they said.

“I’m going to kill you!” said Casiano as he stood with his hands in his pockets, according to the sources.

When the cops tried to grab him, he took off. Casiano ran six blocks with cops in tow and jumped into the Harlem River at 181st Street.

Harbor units responded, fished him out of the water and cuffed him. He was taken to Harlem Hospital for treatment to scrapes on his legs. Charges were pending.

Arhenis Baptista, the man cops were arresting when Casiano tried to intervene, was charged with drug possession,obstructing governmental administration and resisting arrest.