A bystander was seriously wounded and a suspect shot three times Friday by undercover police investigating illegal firearms sales in Mount Vernon, authorities say.

The shootings occurred at about 4 p.m. in a residential neighborhood near Beekman Avenue and Pease Street

An undercover New York Police Department officer met with a suspected illegal-gun dealer in the Bronx and the two men drove to Mount Vernon to conduct the transaction, investigators said.

When they arrived, a second suspect entered the back seat of the car and pointed a gun at the officer's head and demanded cash, police said. The officer handed the gunman some money and he attempted to flee.

The officer signaled his backup team and started to chase the gunman who turned and pointed his weapon at them, investigators said. The officer shot and hit the gunman three times in the torso.

A 63-year-old bystander, standing behind the gunman, was also wounded. He was transported to Jacobi Hospital where he was listed in serious condition, police said.

Information about the condition of the wounded suspect wasn't available.

Police recovered a replica of a large-caliber gun at the scene and were searching for the other suspect, investigators said.

