I don't find that conclusive. After the 1:50 mark and gunfire is heard, the people are still looking toward Mandalay Bay even though they are very close to the cop who was supposedly firing at them, and then at the end you see a cop again looking around. It seems to me more that the cop was in a crouching position with his weapon drawn, not sure what was going on or where the shooter was or where other potential shooters might be. It also doesn't appear that he's holding an automatic weapon that can fire that fast.