What causes my wheels to not be able to roll when I put in drive? on 1992 GMC Safari

Won't drive forward nor backwards and brake pedal will hardly push

Asked by for the 1992 GMC Safari
If it is like this ALL the time even without engine running and brakes never release with NO pedal travel, suspect blockage in the brake fluid circuits, fluid cant return! Most likely the master cylinder needs to be replaced and system flushed. Fluid dirty, black in color? Have it checked out by a mechanic, not a diy repair, or do you know someone that is pretty car savvy and will help you out with some testing?
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could be brk booster issues or hydraboost depending on how veh is equipped