Myles J. Scannell, Senior Patrol Inspector, Marfa, Texas, was shot and killed on September 9, 1929, on the banks of the Rio Grande River near Polvo, Texas, southeast of Presidio. Inspector Scannell was working alone and apparently was attempting to arrest several aliens. Signs indicated that, while walking with the individuals he had in custody, Inspector Scannell was shot from ambush by someone else. Inspector Scannell's body bore two bullet and fifteen stab wounds. There is no information available concerning whether or not the killer or killers were identified and apprehended.

Inspector Scannell had entered the Service as a Mounted Watchman in September 1921 at Presidio. He was among the first Patrol Inspectors to be appointed to the Border Patrol in 1924, and became a Senior Patrol Inspector in July 1926.