Locks and brakes are separate vacuum systems on that car- Locks are run by the pump in the trunk, brakes off engine driven pump.
If you had to make a hard stop recently, that could have caused the brake failure. In the master cylinder, corrosion builds up in the areas the pistons normally do not travel in. When you stomp on the brakes, the pistons go into this corroded area, and the corrosion (aluminum oxide or iron oxide depending on what the master is made from) cuts the seals allowing fluid to leak past. This results in extremely soft pedal and total loss of brakes in a short time.
For a test, with the car idling, put your foot on the brake lightly. If the pedal slowly drops, then the master is done and needs to be replaced. Having this failure, you should also replace all the rubber flex hoses in the brake system. Chances are they are just as old as the master.