'95 Caprice Classic Wagon porblems

[JGrefenstette]

my parents '95 caprice has the Chevrolet 350 V8 LT1 Corvette engine and the standard auto tranny, think its a 4 spd with overdrive (i asume so because the gear selection is "P, R, N, OD, D, 3, 2, 1")
just recently it has started to do somthing very unusual. one morning i had warming up and got in to go, and as soon as i pressed the brake to put it in gear it cut the engin instanly, and there sounded like a compressor or somthing wistling or letting air out or somthing as the belts slowed to a stop. And i thought this had somthing to do with the fact that the radio was on because it did it again in the exact same situation with stereo on.
But just as i though i was narrowing it down, it shut out on me as i was slowing to a stop light. the stereo was on for this time too. I was going between 20-30 when i presed the brake pedal, and i totaly cut out. But then i was leaving work and had it idling with the radio off. got in, pressed the brake..... shut right off! I got no idea.

does anybody have any clue as to what this could be and or a solution.
this type of problem is very unsettling
and one more thing... i got on it pretty good few days ago (not too hard, didnt go to the floor with it) and it seem to not no when to shift. it felt like it stayed in 2nd way way too long, then it almost felt as if it droped streight to 4th cause if it hit 3rd there was really minimal power from it (like in a manual if you wynd out a gear then just go to the next, your still at pretty high rpms and have good power, but if you skip right to the gear after the next you feel the rpm/power loss). could this be an indication of anything? or caused anything?

i would really apreciate any help guys. i dont like these type of problems, specially since its the parents car.
id love any advice and or solutions
thanks a lot
jimmy