Motor knocking

What is your question?

I recently purchased a used 2005 Cadillac CTS, after about a week of driving I was driving down the highway and car shits off, tried jumping it off and luckily got it home {car starts making a knocking noise in the motor}After looking I realized no oil in the motor, so I add oil and the car starts and runs but it continues to make the knocking noise any suggestions

What makes this problem better or worse?

Car will shut off after about 20 minutes of driving

How long has your 2005 Cadillac CTS had this problem?

A week