A No. 2 train turned into a deathtrap for two young men fatally stabbed by a vicious thug who thought he had been dissed, cops and witnesses said.
The bloody battle erupted after the victims tossed a trash bag that accidentally hit another man who flew into a rage and whipped out a knife about 5 a.m. Sunday, witnesses said.
"He...went right for a knife in his jacket," Bryan Woods, 24, a pal of the slain victims, said after speaking to cops at the NYPD's 6th Precinct stationhouse.
Woods said his friends tried to apologize to the man - who was still at large last night - but his rage could not be stopped.
"We said, 'You're going home. We're going home. This doesn't have to get so serious,'"
"He felt threatened. We kept trying to calm him down. Then everybody started brawling at the same time."
The knife-wielding assailant stabbed Ricardo Williams, 24, and Darnell Morrell, 24 - who boarded the train in Times Square - leaving them to die in pools of blood.
As the train rolled into the W.14th St. station, the victims' pals pushed the madman onto the platform.
His hands covered in blood, the killer tried to jump back onto the train, but the doors closed quickly and the train pulled away.
"When we left, he stood banging on the glass [train window] with the knife in his hand," said Woods, who had dried blood on his clothes hours later.
"[He was] laughing like he knew he got one of us."
Cops were still hunting the killer last night. Two men were questioned in connection with the subway slaughter late Sunday but then let go, police sources said.
The killer and his crew were already riding the downtown train when Woods, 24, of Brooklyn, and a group of friends hopped on at 42nd St. after leaving a party, police sources said.
As the train, which was making local stops, pulled into one of the next two stations, Woods said, the doors opened and one of his companions threw a bag of garbage at a receptacle on the platform.
The errant toss instead hit the knife-toting thug, who was standing near the door. He went berserk.
The death train was finally stopped by cops at Houston St., where paramedics found Williams and Morrell lying mortally wounded inside the subway car.
Both had been stabbed multiple times to the torso, police said.
Morrell's friend Brittney Cesar, 22, of Brooklyn, mourned the loss of a "fun person to be around."
"He's not a fighter," Cesar said of Morrell. "He really didn't deserve this. They took away a good person."
Sheila McDonald said her son, Deshawn Pearson, grew up with Morrell and Williams in Flatbush and was with them when they were killed.
"It was senseless," said McDonald, describing Morrell and Williams as "good boys who grew up at my house."
"My son called me at 6 in the morning crying and screaming that his friends had died."
Rose Clarke, 24, said her brother was a friend of Williams and was on the train when the fight erupted.
"He was funny," Clarke said of Williams. "When he was dying, he was smiling."
A third man, Mark Joseph, 23, was sliced in the back of the neck and stabbed in the arm and was in stable condition at St. Vincent's Hospital Manhattan Sunday, police said.
Woods said Williams was murdered shortly after one of the happiest moments of his life.
"He just got engaged last week," Woods said.
Another of Williams' close friends who witnessed his tragic death took to Twitter Sunday to vent his frustration.
"They...killed my best friend," the pal wrote. "I can't stop crying. I actually watched my best friend die yo! This...is crazy!"