Missouri police say an off-duty officer fatally shot a man who was trying to enter the officer's home, and a relative says the two had been arguing on Facebook about the Black Lives Matter movement.

St. Louis County police say 20-year-old Tyler Gebhard threw a concrete planter through a window to enter the officer's Lakeshire home Saturday evening. The officer, who wasn't identified, then shot him.

Police say Gebhard was known to the family and had recently made online threats toward them.

An uncle of Gebhard's, Patrick Brogan, of Waterloo, Illinois, told The St. Louis Post-Dispatch (http://j.mp/29r2hhC) Gebhard and the officer had been arguing on Facebook. He said Gebhard, who was biracial, empathized with the objectives of the Black Lives Matter group.

Police Chief Jon Belmar says the officer is on leave.