Head over to John’s house at Pronghorn Ranch and speak to Abigail to begin this mission. Abigail suggests that John take Jack with him to pick up the mail in Strawberry. Follow the marker along the road and John will hand over the reins to Jack in order to teach him how to drive. Once you arrive in Strawberry, get out of the wagon and head into the Post Office to inquire about his mail. Back on the wagon, John hands the reins over to Jack again to have him drive them back to the ranch. Along the way, you can have Jack speed up or slow down by targetting him and pressing the corresponding button.
Eventually, John will notice a tail and gives Jack directions to pull over at the nearby fallen tree. As John goes to meet the three men, ignore the chance to difuse the situation as nothing can be done about it and enter Dead Eye, you’ll need to score a headshot on all three men during one Dead Eye sequence. Skip the following cutscene if you’re going for the Gold Medal and then you’ll need to race back to Pronghorn Ranch as quickly as possible. The time requirement here is harsh and you’ll need to cut corners where you can to save every second.