A 16-year-old boy was slashed on the staircase of the luxury Upper West Side high-rise Wednesday night by a crew of four attackers, according to law enforcement sources and a neighbor.
The knife attack unfolded at about 10:45 p.m. inside Waterline Square, where residents are offered a number of flashy amenities and market rent for a one-bedroom unit starts at around $7,000 per month.
“It’s crazy though, there are millionaires that live here, then there are these young kids coming here from the projects, hanging out, pretending to be gangsters or whatever,” building resident and witness to the attack John Him, 23, told The Post.
“They leave me alone pretty much, but I always check on my Caucasian friends to make sure they’re OK,” said Him, who is black…