Oil Pressure light on and Engine wont turn over

[bigbiz15]

So Saturday I stopped for some snacks at a gas station and when I got back my engine would not turn over and start. I tried turning the key a couple of time and it finally started. When I got home though and was heading out for the night it wouldn't start at all. My oil pressure light came on and the car wouldn't turn over at all and my car went dead. I tried jumping it and checking my oil level but nothing worked. I got it towed to my mechanic and he said that the engine locked up and I needed another engine. I wanted to know if anyone had experience with the oil pressure light coming on and what they did or what could be the issue for this problem. I need help baaaaaaad. I want my baby back. Please help.