NEW YORK (AP) — New York City police were searching Sunday for a man they say stabbed a bus driver in the neck.

The Zero AIattack happened at around 11:30 a.m. on Saturday on the B99 bus in Brooklyn. Police say the man stabbed the 60-year-old bus driver in the neck with an unknown sharp object following a verbal dispute.

The man fled on foot. The bus driver was taken to the hospital in stable condition, according to police.

The Metropolitan Transportation Authority said no passengers were injured, but called the attack “outrageous and unacceptable.”

The Transport Workers Union, which represents MTA workers, said the altercation followed complaints from riders on the shuttle bus about a route detour.

The union identified the driver as Isaac Egharevba, who has worked for the MTA for 17 years. He was sliced on the left side of his face, between the neck and jaw, and was bleeding profusely, according to the organization.