Can I get fired for getting cancer?

I live in Arizona and my roommate found out he had a brain tumor. The brain tumor turned out to be cancerous and he's undergoing radiation and chemotherapy. During surgery, he had a stroke that left his right side semi paralyzed. He is unable to return to his job which required him to be ambulatory and dextrous. He has already used up sick and vacation time and the 12 weeks of FMLA leave required by federal government. They now want him to sign a paper that would allow him 30 days of unpaid absence and then he agrees that he is terminated. He cannot return to work in three weeks (according to his physician). Is this legal? Does anyone know his rights? It's Arizona, so a right to work state.