Three officers in Baton Rouge were shot and killed in an apparent ambush Sunday morning, less than two weeks after a fatal police shooting sparked protests in the city. At least four others were injured in the shooting, Baton Rouge Mayor Kip Holden said. He said the officers were responding to a call of shots fired when they were gunned down. Baton Rouge has been roiled by protests since white officers shot and killed Alton Sterling, a 37-year-old black man, on July 5. Four people were arrested last week in an alleged plot to kill police officers. Louisiana Gov. John Bel Edwards condemned the 'unspeakable and unjustified attack' on law enforcement.