A man died after sustaining a head injury while riding between subway cars on a 4 train in Manhattan Sunday night. Riders saw him fall and dragged him into the last car where they tried to stem the blood flow, to no avail.

"Folks, whatever you do while riding the subway, please do not attempt to move between cars while the train is moving," 41-year-old passenger Alexander Daniyan tweeted, along with a grisly photo of the gravely injured victim, his face obscured. "This poor soul did, and now he's no more..."

According to Daniyan, the man was making his way from one end of a southbound 4 train to the other. "He was wobbling, but he wasn't falling over," Daniyan—who was traveling in the second-to-last car—recalled. When the victim exited Daniyan's car, the door closed behind him, and that's when he stumbled.

"Some people heard, some people saw, whatever, we noticed he fell," Daniyan said. "The people closest to him immediately opened the doors and lifted him up. I was right behind them."

At first, the riders didn't realize how serious the man's injuries were. "Then we laid him in the next car," he continued, and "blood started gushing out, on the floor of the car and the median, the whole nine yards. At that point I was like yikes, this is something else."

Daniyan called 911 around 10:20, when the train pulled into its stop at 14th Street-Union Square. He said the man had a hole in the back of his head, and "some of the passengers tried to block it with ... newspaper and a t-shirt." Another passenger mentioned he could feel the man's faint pulse.

The NYPD says officers arrived on the scene shortly before 10:30 p.m., responding to reports of an unconscious male in the station. EMS took the unnamed 33-year-old victim to nearby Beth Israel Medical Center, where he was pronounced dead. The cause of death has not yet been confirmed, and the MTA had not responded to our request for more information. We'll update when we find out more.