Let's start with the man in the yellow suit. A previous answer stated that Mae shot him. That is incorrect. The man in the yellow suit wants to take Winnie and expose the Tuck family's secret of immortality. Mae Tuck is absolutely unwilling to let that happen, so she attacks the man by hitting him in the head with the stock of a shotgun. The blow to the head doesn't immediately kill the man, but he does die shortly after:
"You ain't going to do a thing like that to Winnie. And you ain't going to give out the secret." Her strong arms swung the shotgun round her head, like a wheel. The man in the yellow suit jerked away, but it was too late. With a dull cracking sound, the stock of the shotgun smashed into the back of his skull. He dropped like a tree, his face surprised, his eyes wide open.
Mae Tuck is arrested for her actions, and she is thrown in jail. Additionally, because the man in the yellow suit died, Mae is likely to be hanged as punishment. That won't be good because people will see that she is immortal. The Tucks hatch a plan to break her out of jail, and Winnie helps out by switching places with Mae. The plan is successful, and the Tucks once again leave the town. Winnie is in some trouble, but nothing really comes of it. She decides to not drink the water that will grant her eternal life, and she lives a full and complete life and dies of old age.