Piper Lee, 41, faces up to 20 years in prison on charges of aiding and abetting the assault of a federal officer and one count of possession of stolen mail. He will be sentenced Nov. 1.
Two others, Bradley Ahearn, 24, and Sarah Richford, 27, were also charged in connection with the incident.
Ahearn pleaded guilty to all charges in the shooting of a mail carrier in Spring Branch, Texas, on Feb. 11, 2017. Ahearn and Richford both fled the scene with stolen mail.