Returning home on Saturday night after a dinner in Manhattan with some longtime friends, Gregory Locke boarded a No. 1 subway train and was confronted with an ugly sight.

The car’s windows and posters were covered in anti-Semitic graffiti, according to accounts from Mr. Locke and another passenger in the car, Jared Nied. Messages like “Jews belong in the oven” and “destroy Israel, Heil Hitler,” had been written over subway maps, as shown by photographs taken on the train. Swastikas were drawn in black marker on the doors and windows.

Mr. Locke, 27, a New York lawyer, said in a phone interview that his first reaction was shock, “especially once I realized how many instances of graffiti were on the train car.”

“But the shock quickly subsides and turns into a sort of a realistic horror,” he said. “You realize it’s appalling but it’s also not surprising at the same time.”