Fired for needing brain surgery

I went to the doctor today after having headaches and was told I need emergency surgery this Monday and will be out of work for 4 weeks. On the way back from the doctor, I stopped by work and told them about the surgery, and was then let go as "they need someone to fill the place." Fmla would not kick in until 10/17 of this year but I will not survive without immediate surgery. I am in virginia. Is there anything I can do to stop this? I'll be unable to pay bills and they are dropping the insurance i am using to pay the surgery. Can I be fired for needing an emergency surgery?