Police in the US state of Iowa say they have arrested the suspect in the "ambush style" killing of two police officers. He has been named as Scott Greene, a 46-year-old man from Urbandale, a suburb of Des Moines. The first officer was found shot in Urbandale yesterday. <br/><br/>The second was found 20 minutes later several blocks away. Both were sitting in their patrol cars when they were attacked. The fallen policemen have been identified as Urbandale officer Justin Martin, 24, and Des Moines Sgt Anthony Beminio, 38. The motive for the attacks is unclear.<br/><br/>Speaking at a news conference, Sergeant Paul Parizek of Des Moines Police said there definitely wasn't an opportunity for these officers to defend themselves or respond to the attack. Both officers were seated in their cars and were shot while they were sitting.