After the murder of two NYPD officers on Saturday, the outspoken head of the city's primary police union blamed protesters and Mayor Bill de Blasio for the deaths of Officers Wenjian Liu and Rafael Ramos.

"There's blood on many hands tonight," NYC Patrolmen’s Benevolent Association president Pat Lynch said Saturday night, ratcheting up already frigid tensions between City Hall and One Police Plaza.

Lynch blamed those who "incited violence on the street under the guise of protest," -- a reference to the swell of demonstrations in New York City and across the U.S. in the wake of a grand jury decision to not indict a New York police officer for killing an unarmed black man, Eric Garner, earlier this fall.

Lynch then went after Mayor de Blasio: "That blood on the hands starts on the steps of City Hall, in the office of the mayor." He went on to praise the fallen officers, and said that those responsible for the killing will be held responsible. (Video above.)

Officers Liu and Ramos were shot dead "execution style" while in their patrol car on Saturday afternoon in Brooklyn. Ismaaiyl Brinsley, 28, ambushed the officers, ran away to a nearby subway station, then committed suicide by shooting himself in the head.

The PBA has been highly critical of the mayor's stance on police tactics and his support forprotests about police brutality. The union has also asked its members to ban the mayor from attending officer's funerals.