A five-year New York Police officer is fighting for his life after being shot Saturday night during a robbery, officials said.

The veteran officer, who was off duty at the time, attempted to buy a car on Ruby Street in Brooklyn after the details of the purchase were arranged on social media, police said.

When the officer arrived, the suspect immediately displayed a gun and announced the robbery, police said.

Gunfire was exchanged, the officer was hit and taken to the hospital where he is in critical condition.

Mayor Eric Adams said that the officer was conducting a simple errand and was shot. Adams said that they would catch the person responsible for the attack.

ABC News' Darren Reynolds contributed to this report.

This is a developing story. Please check back for updates.