In Chicago, four people were arrested Wednesday after a disturbing video posted to Facebook shows them torturing a bound and gagged man while shouting, “F— Donald Trump!” The video shows two men and two women—all of them African-American—cutting the man with a knife, burning him with cigarettes and threatening him with murder. The victim was identified as an 18-year-old white man with mental health challenges. The attackers were also teens. The video spawned a backlash on social media, with many white supremacist groups blaming the Black Lives Matter movement for the assault. The hashtag “#BLMKidnapping” began trending on Twitter by Wednesday night.