Why is the pOH of 1M HCl 14? Why is the pOH of 1 molar HCl 14 in an aqueous solution?

I was learning about strong bases and strong acids in chemistry within this context:

We have 1L of pure water at 25°C, and the pH of water is 7 and the pOH of water is 7, so it is a neutral solution. 

Then we add 1 mole of HCl into the water. HCl, because it is such a strong acid, disassociates completely in the water. After some basic calculations, we found that the pH of HCl was 0 and the pOH was 14, but the way he showed this was using the water's pH and pOH - does this make sense?

So we found that the pH of water is 0, and then he did something funny and got a pOH of 14. Why is the pOH of this solution 14?

Here is the video, video mark, 10:02: Khan Academy - pH &amp; pOH of Strong Acids and Bases
In the moment from the video that you referred to, Sal was using the equation $\rm pK_w=pH+pOH$ to find the $\rm pOH$ of the solution. $\rm pK_w$ is equal to 14, since $K_w$ is equal to $1\times 10^{-14}$, giving us the new equation $14=\rm pH+pOH$. We know that the $\rm pH$ of a 1M solution of $\ce{HCl}$ is zero from earlier on in the video. This gives us that $14=0+\rm pOH$, or in words, that the $\rm pOH$ must be equal to 14.