The eagle-eyed plainclothes cops Officer William Haut, Sgt. Clyde Jasmin, Officer Jazmin Roman and Officer Bonlei Wong made the arrests after spotting the suspects Monday and Tuesday.
Before Tavon Silver, 32, was discovered unconscious while aboard a southbound 4 train that had just reached the 14 Street/Union Square station, and later pronounced dead, he was stabbed last year in a homophobic attack, sources said.
A straphanger was stabbed on the J train in Brooklyn while trying to help a fellow passenger early Sunday morning the second knifing on the train line in a matter of days, sources said.