can my empoyer get away with this? what should i do?

it started over a few months ago when i filed a osha compailnt anomynously about several safety violations.
after they contacted him, he then fixed some but not all of them. i then discovered some more violations that i found were hazardous to mine and my co workers health. so i first went to my employer to tell him i would appreciate them being fixed. he said he would and never did. i brought it to his attention again told him i would have to file a complaint if he did not. he said he was on top of it. all of a sudden a few weeks later he cam to me and said that there was no place for me here anymore and he was going to have to let me go. i was fine with this, but when i tried filing unemployment he appealed saying that he did not fire me and that i quit. if i was the only employee present at the time, how can i prove that i was really fired? what should i do?