Authorities in New York City and Philadelphia say the same person may have been responsible for shooting an on-duty Philadelphia parking authority worker and a Bronx gas station employee three days apart last month.

Police released video and photos showing a man walking up behind a Philadelphia Parking Authority enforcement officer as he was writing tickets and shooting him shortly before 4 p.m. on Nov. 25 in the Frankford neighborhood .

The 37-year-old victim was hit in the neck and was later listed in stable condition. Police announced $20,000 in reward money and said the suspect should be considered armed and dangerous.

Capt. John Walker told The Philadelphia Inquirer that New York City police contacted Philadelphia police “immediately” after the department released images and video. New York City police video shows a suspect approaching the door of a gas station convenience store and firing twice at the man who opens it. The 49-year-old victim, hit once in the left side of the head, remains in critical condition.

Police say the shooter appears to be wearing the same outfit in both crimes. Walker said both shootings were unprovoked and appear random, with no known similarities between the victims — and in both, there is no known motive.

“Just in both cases, they’re working-class people out there doing a job when they’re shot,” Walker said. Since both shootings occurred near elevated train tracks, police believe the suspect could be traveling by rail, he said.