Hello wonderful Volvo enthsuiasts. I've run into an odd problem.

On my way home tonight, after I put my wagon into reverse (to park it) and started giving it a little gas, it began to move backwards (as expected), but shortly after, the whole car began to shake, as if something in the transmission was just locking up. It didn't sound like anything 'popped' or 'whined' or 'grinded'. It just shook violently. I put it in park, not wanting to destroy anything and then put it back in reverse and tried to back up again, only this time, it just revved as if it was in neutral. Unfortunately, the car is now inches away from a wall and even after I put the car in neutral, it won't budge. It's as if its in park, but will roll forward, but will not move backwards at all.

Now I'm stuck with my car that can go forward, but is inches away from a wall and cannot move in reverse...

As it is 12AM right now, I'm saving most of the diagnostics until tomorrow.

What I have checked is:
1. There are no leaks anywhere
2. E-brake handle is down (will check the actual condition of the brakes themselves tomorrow)
3. The transmission "appears" to shift between the gears fine (meaning the engine will rev slightly when switching through the gears) with no unusual noises (at a stop of course)
4. The transmission fluid is in good condition and is not low
5. From what I can tell the rear brakes have no visual damage on them nor are they extremely hot or smell (as if the brakes locked up).

What I am hoping for is some direction. How can I lose reverse while still having the ability to move forward if its a transmission problem? How can it be a brake problem if I drove the car 30 miles home without feeling like the e-brake was on?
P.S. There were no codes either, fwiw.

Appreciate any help/suggestions!