It’s a concern every New Yorker has tucked away in the back of his or her mind: What would happen if I were to fall or get pushed on the subway tracks? On Monday, that nightmare became a reality for one NYC resident, and police are saying it happened at the hands of another “deranged” passenger. And now a picture shows the moments before the man’s death and authorities have released video showing what they believe is the argument that led up to the alleged murder.

The victim, 58-year-old Ki-Suck Han of Queens, was at the 49th street station near Times Square when he apparently confronted another passenger who was “acting crazy,” according to WPIX-TV (there is also a report that Han may have left his home earlier that day angry and intoxicated). That conversation went south in a hurry, and the man eventually threw Han onto the tracks as a train approached. Han frantically tried to climb back on the platform, but to no avail.

Freelance photographer R. Umar Abbasi ran toward Han and started firing his flash in order to get the train to stop.

“I just started running, running, hoping that the driver could see my flash,” Abbasi told the New York Post.

The train did slow down, but it could not stop in time. Abbasi said it eventually “crushed him like a rag doll.”

You can see the incredible, heartbreaking photos Abbasi captured moments before Han’s death in the video report below:

But that wasn’t the only image captured as the incident unfolded. One bystander captured the argument between Han and his attacker and turned it over to police, and authorities have now released it in hopes of identifying and capturing the man:

The Post details what exactly happened:

The horrific drama unfolded after Han approached the crazed man — who police sources described as a panhandler and witnesses said had been harassing and cursing at straphangers — on the southbound platform and tried to calm him down.

As other riders congregated toward one end of the platform, Han and the man were about 100 feet away from them.

“He went up and tried to calm him down, saying, ‘You’re scaring people,’ ” a law-enforcement source said.

“The emotionally disturbed guy just started screaming and cursing, saying, ‘You don’t know me! You don’t know who I am!’ ”

As the train’s arrival was announced over the loudspeaker, the attacker “just grabbed [Han] and launched him — just threw him — straight onto the tracks,” a witness said.

The killer then grabbed a paper coffee cup he used to collect change — which he’d put down before the assault — and fled.

A second-year doctor in residence, Laura Kaplan, was also on the platform at the time. When she saw Han get hit, she rushed to help. But it was too late.

“I heard what I thought were heart sounds,” she told the Post. But he never responded.

“There was blood coming out his mouth. We couldn’t do CPR. He wasn’t in the right position. and there was just no way to get him out of there.”

“People are just standing there in fear and shock, not really knowing what’s going on,” Patrick Gomez, another bystander, told WNBC. “Some people started running out of the platform, others just stood there.”

Similar assaults — where someone is deliberately pushed onto the tracks — are rare, but they do happen. As WNBC notes, the most high profile one happened in 1999, when a mental patient admitted he pushed Kendra Webdale to her death. That led to “Kendra’s Law,” which allows authorities to monitor patients outside facilities to make sure they’re taking their medicine and aren’t a danger.