Hey I have a 2010 Ford crown Victoria police interceptor with a 4.6l with a 4 speed automatic that has 156,700 miles

I bought my car two weeks ago it was running like a dream I decided to check the oil and the oil was black so I decided to change the oil the next day. On my way to work there was a knocking sound when I accelerate and let off the gas and gets louder with rpm. So I babied it home when I got off, but then the red oil light came on the oil was full so it was telling me oil pressure was low. I got home then changed the oil put in motor craft synthetic blend and new filter and gasket. After the oil change the knocking sound was still there and my oil light would come on after accelerating up to speed on and off. And today my engine when coming to a stop at a stop sign died on me had to push it off the road. I gave it a few minutes and tried starting it in neutral and started up and got it home to park it only a 1000 feet away. Any ideas what it could be, my guess is bad oil pump or cam/crank position sensor please help