[lacrew]

"And his reference for this is ..."

...Thin air.

Per the link below, "Paddock, an avid gun owner, was known to come into the firearms store on a regular basis — typically to have his rifles cleaned..."

IOW he was firing his rifles somewhere, and likely became proficient with them.

http://nypost.com/2017/10/04/vegas-shooter-seemed-upbeat-while-buying-guns-last-week/

[Sacajaweau]

Read there was a place in the dessert not too far from his home where shooters regularly went.

There's another of his friends/associates who was shown his "gun room".

One of the dealers said he was no novice.

Girlfriend was in the car while he was making a purchase. (She knows soooooo much more...but not about the event itself.)