U.S. Attorney General Merick Garland said on Monday the Department of Justice is opening a probe into police practices in Louisville, Kentucky, including how the police department serves search warrants on private homes after Breonna Taylor, a Black 26-year-old woman, was killed in her home last year during a search by Louisville police officers, sparking civil rights protests nation-wide and raising concerns about the constitutionality of the controversial "no-knock warrant" used by police in this case.