Four sick bastards got busted in Chicago for allegedly tying up and torturing a white guy ... and they broadcast the whole crime on Facebook Live.
The suspects are all black and shouted "F*** Donald Trump" and "F*** white people" repeatedly during a 30 minute video that showed them harassing and tormenting the victim ... even cutting his scalp, leaving him bleeding at one point.
The victim is an 18-year-old from a Chicago suburb. Police say he is mentally challenged, and had been reported missing. He was found disoriented Tuesday, and cops later connected him to the disturbing social media clip ... which led them to the suspects.