DES MOINES, Iowa — A white man with a history of racial provocations and confrontations with police ambushed and fatally shot two white Des Moines area police officers in separate incidents Wednesday morning, police said.Authorities took 46-year-old Scott Michael Greene into custody hours after the killings and less than three weeks after he argued with officers who removed him from a high school football game where he had unfurled a Confederate flag near black spectators.Greene flagged down a state Department of Natural Resources employee in a rural area west of Des Moines, identified himself and asked that he call 911. Sheriff’s office and state patrol officers responded and took Greene into custody.He’s suspected in the early morning killings of two officers, who were shot as they sat in their cars. Police identified the men killed as Officer Justin Martin, who had been with the Urbandale force since 2015, and Sgt. Anthony “Tony” Beminio, who joined the department in Des Moines in 2005.Greene was taken to a hospital for treatment of unknown health issues and will be brought later to Des Moines police headquarters, where he will be questioned and charged, Sgt. Paul Parizek said.