How could loomis be deceitful in Z for Zachariah?

In this novel, Mr. Loomis becomes a tyrant over Ann to the point where she feels she is no longer safe living in the same house with him. Mr. Loomis dictates what should be planted in the fields, how they should be planted, and where. Mr. Loomis dictates as well how Ann should spend her time. Mr. Loomis even decides that Ann needs to live with him as his lover. Mr. Loomis goes so far as to attempt to shoot Ann in the leg to make her stay with him.