St. Louis school shooter failed a background check. Why didn't police take his gun?

ST. LOUIS — Police officers were called to the home of Orlando Harris on Oct. 15, nine days before he went on a shooting rampage inside a St. Louis high school. Harris’ mother had asked officers to remove the weapon, an AR-15 rifle, from her home, citing her son’s mental health struggles. Police had been called to the home before. St. Louis police had also been informed that Harris, 19, recently failed a federal background check when he tried to buy a weapon from a local dealer. So why didn't police confiscate the AR-15 before Monday's attack at Central Visual and Performing Arts and Collegiat...