When starting my son's car there is no noise at all. There is no click-click-click, or the engine trying to turn over, nothing. We jump started the car and then it did run, but it did not hold the charge after running 20 mins. Is this most likely a dead/spent battery or something else. (bought the car used with no record of battery age)
Also when we jump started the car there was a 6 inch spark that flew from the battery terminal.

I've had the same thing happen to me (along with about everything else, when it comes to cars).

Usually, it's been the battery in those cases, though at least once, it wasn't the battery that was bad, it was the starter instead. And if other things are happening, like the blinkers are much slower, headlights dimming, etc, it could be the alternator is not functioning correctly.

Since you were able to jump start the car you've pretty much ruled out problems with the starter. If the alternator is bad you should have a warning light lit on the dash. The most likely alternator problem would be a bad voltage regulator module in the alternator.

My guess is that the battery is fried. I recently read an article which said that the maximum life one can expect from a standard lead-acid battery is about 4 years. Warranties notwithstanding. More exotic batteries, such as gel construction, can last a lot longer but they are very expensive relative to a lead-acid battery.

That six-inch arc you describe does concern me but I have nothing to offer as to why it happened except for the possibility that the jumper cables weren't properly grounded.

Let us know what the fix turns out to be.

Thanks guys! It was the battery, he put in a new one and its running fine now!