Reddit, I have a question of BBQ ettiquette. Who was in the right?

Chad states that he is doing the BBQing. He asks everyone how they want their steaks. It is known that he will start the BBQing in 20 minutes when the potatoes are near completion. Tom then comes in and turns the BBQ on, without Chads knowledge. He then goes and grabs the steaks puts them on, and says to Chad, who is across the yard " I thought you were doing these Steaks?" Chad does not go and help, because the BBQing is underway, and he doesn't know where the steaks are in their cooking process, and doesn't want to intrude on the BBQ process. (The steaks have been flipped.)

Once Tom has started BBQing, is it his responsibility to continue the process? Or should Chad have stepped in and taken over his duty?

Note: Tom is an older gentleman, and Chad is the step son to the BBQ host.