Who is Mr. John Loomis from Z for Zachariah and what is their importance?

Mr. Loomis, the novel's antagonist, is a scientist who worked with a team who invented a material that repels radiation. The group made a suit out of this material, as well as a filter for water and containers for food. The team was waiting for the military to come inspect the invention when war breaks out and the United States is devastated by a nuclear holocaust. Mr. Loomis is locked in his lab with another scientist. This scientist wants to take the suit and find his family, but Mr. Loomis refuses. Mr. Loomis kills his co-worker when the man refuses to back down.

Mr. Loomis waits for a few months and then he uses the suit to leave the lab and search for other survivors. Mr. Loomis finds Ann's valley and takes up residence there. Unfortunately, Mr. Loomis takes a bath in a radiated stream and becomes very ill. After his illness, however, Mr. Loomis focuses on the future and begins treating Ann like a possession. In the end, Ann tires of Mr. Loomis' tyrannical ways and leaves the valley with his suit.