Because of Roy's involvement, Luke's relationship with Selina and her five children had become worse. He was resentful of Roy, and now because of the punch he finally had a place to vent his frustration.
Before Roy gave him another punch, Luke pulled his arms and then threw him to the ground.
Roy did not expect that Luke could react so fast, but he had learned fighting since he was a child, so he also made a quick reaction.
Inside the room, Selina was not asleep. She heard the noise, and after opening the door she saw two men rolling around on the floor. Both of them had injuries, but...