HOW DO WE KNOW IT WAS PADDOCK?

Because the authorities say so.

8 guns found in his room, after the shooting (How did he sneak them all in? And why so many?)

And apparently no known motive, or political affiliation.

So again: how do we know it was Paddock?

Because the authorities say so.

And the shooting went on for 10 minutes.

Open carry would not have stopped this guy (if it was him), nor would a ban on automatic rifles.