Oil leak

First place I would look is the drain screw ,, they may not have tightened it with last oil change and it may have gradually worked it's way out

Agree with Tom. Add some oil and watch drain plug in pan if that leaks you found your culprit. Hopefully it's not a rear main seal.

Look at the oil filter area also. One more thought...you didn't blow the engine up and toss a connecting rod through the oil pan did you?

Comman leak areas are as follows on the 2.8L engines, Head covers, Cam seals, Crank seals front and back (might be one of these), oil pan (usually very easy to ding the oil pan and create a crack), drain plug (the copper or aluminum washer can ad will ware out over time), Oil filter, oil filter housing. These are all the comman oil leak locations. I would guess you either have a lose oil pan screw or filter first myself as well but check the pan for signs of damage. I cracked my 2.8L on a parking lot side walk once and i barely touched it. the second place i would guess is the oil filter houseing as it can some times come loose and begin to leak, replacing it will often fix it.