When Nick is using Catherine's earring to demonstrate to Sara how easy it is to forge checks, Nick has the earring in his left hand when he starts poking at the paper, but it changes to his right hand in between shots.
The 1st shot damaged the newspaper used to conceal the weapon, but the following shots showed an undamaged newspaper.
The hitman's gun was concealed by a newspaper. The gun was a semi-auto so it is unlikely that he would get six shots off without a spent casing becoming jammed in the ejection port (shooting enthusiasts call this a stove-pipe). The paper would had prevented a casing from clearing the slide and no follow up shots would have been possible until it was cleared.