my sister is bipolar. when she is angry or annoyed, there is virtually no stopping her. she doesn't think and she often regrets and overthinks the siutation afterwards. it sounds similar to what you are describing here.

it could be possible that he wasn't ignoring you- maybe he did not hear. I think next time, it would be an idea to follow him upstairs, and give him a gentle but firm reminder. if he is getting you angry, wait a while, take a breath, and think the situation through. then work it out with him, "are you going to find a chance to mow this evening? and if not, when do you think you will be able to?" sry, dont know how much help this is.