Background Pony #5252
Knife makes sense as a backup, but holding it together with a pistol does not seem to make sense.
This is SIG MCX. It's inspired by AR-15, but it's a different gun. For example it has no buffer tube (which allows the stock to be foldable/detachable/etc.) and it has a short stroke gas piston instead of a direct impingement system.
In this case the barrel is really short, so the gun would be classified as a short barreled rifle. It's possible that it's chambered in .300 Blackout instead of .223 Remington.