Clyde Barrow and Bonnie Parker were killed by a posse in an ambush in Louisiana. The posse consisting of Texas and Louisiana peace officers was lead by Texas Ranger Frank Hamer. But it was not a roadblock type ambush as implied by a question in Cool Cwiz.
Ivan Methvin lured Clyde into the ambush by removing a rear tire on his pickup to make it look like he was changing a flat tire. When Barrow stopped to see if he needed assistance, the posse opened fire. Methvin did this as part of a deal to keep his son Henry, a member of the Barrow Gang, out of jail.
Related Fact: In 1933, a .45 slug would only make a dent in the metal of cars build by the Ford Motor Company.