Q: My brake fluid is leaking rapidly (in about 3 minutes) out of the rear right tire.

My Dodge Neon recently had full maintenance about 1 month ago, the brake pads are new and fine, however recently my brake light came on, my first instinct was "something is up with my parking brake" but then suddenly my brake required a full depression to even slow the car and once it did it jerked to the right, I then checked my fluid and it was near empty, so I purchased some dot3 fluid (as per specifics) and filled it up, but within 20 minutes it was drained. I refilled figured I had a leak and that I could manage it, as I prepared to drive to the nearest mechanic my brake light was already on and my brakes weren't working, I had only just filled it less than 5 minutes ago and it was empty. I then noticed a large pool around my back right tire, I believe its possible a bleed valve may be left open from the mechanic or possibly something like that, but I'm not at all knowledgeable in cars, please help. I hope this is enough information to help.
My car has an automatic transmission.