Rear wheel locking up?

Purchased this truck used with 27,400 miles on it about 10 days ago. The last 3-4 days I noticed my brakes started screeching. Today as I’m turning into my driveway, my rear brakes seemed to lock for a moment, I pushed the brake down, let off and gave it a little gas - truck rolled maybe 2 feet then locked again. I put it in park, checked to make sure the electric parking brake wasn’t engaged (it wasn’t). I put it back in drive and the same thing happens, rolls about two feet after giving it gas and locks up, I continue to give it a little gas and it snaps out (making a loud noise) then locks back up again... I’ve turned the turning brake on and off a few times. I can feel it releasing so I don’t believe that’s the issue. Look at the brake pads while wheel was still on, they look good. Hoping someone can give me some guidance here.