The subway passenger who pulled the emergency brake during a grisly murder over a seat on the D train claims the attacker was unprovoked. Denouncing previous reports that victim Dwight Johnson had struck suspect Gerardo Sanchez during their dispute, witness Vincent Martinez said the victim — a homeless man who traveled everywhere with his bags — had already moved his duffel bag from the chair when the accused killer snapped.

"He was trying to be nice about it, and then 10 seconds later, he got stabbed," Martinez, a 25-year-old security guard who was on his way home from work, told the Daily News. "He was screaming, 'I'm dying, I'm dying,' and there was blood coming out of his mouth and spraying out his neck…Before you know it, everyone is on one side screaming and yelling...The killer was following him and grabbing him, saying, 'You should have let me sit down.'"

Martinez tells the paper he started "banging and banging on the door to where the guy drives the train, but he didn't answer," so he pulled the emergency brake, bringing the train to a halt in the tunnel between the Rockefeller Center and Seventh Avenue stations in Midtown at around 2 am. The motorman then opened the door and Martinez forced his way inside. "I told him, 'Some guy just got stabbed and he's bleeding all over the place,'" Martinez said. "He's like, 'You're not supposed to [pull the brake], you should have just let the train go.'"

The conductor radioed police and restarted the train about a minute later, and cops told the train crew to keep the doors shut until officers arrived. Martinez stayed in the cab with the conductor until the train pulled into the station, and when questioned by police, he "denied pulling the emergency break out of fear he would be arrested, and told cops he didn't see everything," the paper reports.

While many have questioned the decision to lock straphangers in a car with a knife-toting murderer, Mayor Bloomberg defended the choice. "If all the doors are open and everyone runs in every have a murderer back on the street," he said. "[That] doesn't make a lot of sense to me."

Though friends of the suspect say that Sanchez, 36, has been acting strangely and abusing pain medication since a fall at work two weeks ago, Martinez claims that accused killer was looking for trouble. "I don't how much Vicodin you take or Tylenol with codeine he's taking," Martinez said. "He had a steak knife in his pocket. He wanted to stab somebody." According to the Post, the suspect's aunt, Lisa Rivera, 45, agrees. "Oh, no, what did he do this time? Did he finally kill someone? I've been afraid of that for a long time."