Why do Rw and Melvin beat tj up

In Chapter Eleven, TJ tells the children that he went to Strawberry with the RW and Melvin, but Barnett's Mercatile was closed. They said it would be all right to take the gun and just say to anyone who saw them that they were planning to pay the next day. They send TJ, who is skinny, in through a narrow window, and then come in wearing stockings over their faces. While they are trying to break the wall cabinet with an axe, Mr. Barnett comes down to investigate and struggles with Melvin, until RW hits him over the head with the flat side of the axe.

Mrs. Barnett comes down, sees her husband slumped on the floor, and screams: "You niggers done killed Jim Lee!" She struggles with RW until she hits her head on the stove and falls to the floor. TJ is not sure if they are dead. When the Simmses won't take him straight home, TJ threatens to tell someone that they hurt the Barnetts. RW and Melvin beat him up, leave him in the back of the truck, and go to the pool hall. TJ hitches a ride past Soldier's Bridge, in order to avoid the Simmses coming home on Jackson Road, then walked to the Logans house.