This is exactly what I was talking about. He bought at retail very likely with the knowledge he could sell off any "surplus" for a healthy profit. Thus the other people showing up may find none in stock which will encourage them to scramble around and either buy extra due to the difficulty of securing what they needed for themselves buy more to resell the "extra".
Those of us who recall the gas shortages in the 70's know that you could only buy gas on odd dates if your license plate ended in an odd number, or even numbered dates if you had an even plate number. After the shortage some researchers realized that gasoline consumption based on miles driven went down not up and overall production and gasoline sales remained above a fairly static consumption BUT much of that production was in all the tanks getting topped off every other day or stored in our garage or trunk in gas cans. We thought there was a shortage so the we "over bought" and the amount of fuel available was plenty to meet demand it just wasn't at the gas station to be purchased. We by doing what was best for ourselves as individuals made our collective situation worse because of course with every gas station that sold out prices rose on the remaining supplies. Prompting more purchases because the "smart move" was to stockpile more since it was essential and in short supply.
Sound familiar?