A Queens man was shot dead in a road rage incident early Monday by an off-duty NYPD officer, and now the department and state are probing the cop's use of deadly force.

Wayne Isaacs, 37, is a three-year veteran of the force. Around midnight Monday, Isaacs was on his way home after a 4 p.m. to midnight shift in the 79th Precinct when he allegedly cut off another motorist, Delrawn Small, on Atlantic Avenue in Cypress Hills, witnesses told the New York Post

Small, also 37, had allegedly chased the officer, who was driving a 2002 Nissan Altima and wearing civilian clothing, for about seven blocks, until the two were stopped at a red light. Small exited his vehicle, approached the officer's and punched him several times through his open window.

Isaacs reached for his service weapon and fired at Small from the front seat, the New York Daily News reported.

Sources told the Post the officer fired three times, striking the victim twice.

Small died at the scene.

Small's girlfriend, Zaquanna Albert, 35, their 5-month old son and one of Albert’s teenage daughters watched from their car.

A video camera has allegedly captured Small exiting his car, cops say, but the department refuses to release the footage.

Isaacs, who lives in Brooklyn, is now the subject of an internal probe headed by the NYPD and Attorney General Eric Schneiderman.

"The attorney general has determined that this case falls within the parameters of the executive order and has launched a full investigation," Schneiderman said in a statement. "The investigation will be led by Executive Deputy Attorney General and Chief of Attorney General's Special Investigations and Prosecutions Unit, Alvin Bragg."

On whether the shooting was justified, NYPD Commissioner Bill Bratton wouldn't comment.

"It's too early to determine what transpired...before, during and then after the incident," Bratton said at a news coference.

According to the Post, the city shelled out $20,000 to settle a suit after Isaacs and another officer were accused of beating a man, who one of the cops allegedly called a "n-----" on July 6, 2014.