If you had no problems before, it must be the master cylinder. Your brakes are designed so that you should not loose front and back at the same time. The only common part between the two is the master. Now, if you already lost the front or the back before this, troubleshooting becomes a little bit more involved. You would have to have two problems at once if it's not the master cylinder. I did the exact thing you did but with my plow truck. A tree stopped me though. OUCH That's bad for the neck!