Hmmm. If I were in the crowd with my family and somehow armed with a good rifle, I might, but probably not from 1300 feet, 30 stories up.
If I were in a closer position with my family and a hunting rifle, and he wasn't shooting at us, I'd probably seek cover.
If I were a cop in a position close enough to shoot at him (no threat to my family), I don't know. I have no idea what their training is in such situations.
BTW, did you read somewhere he was leaning out the window? I hadn't heard that.
If he was shooting down into a crowd 320 feet below and 1300 feet down range, I guaranty he he was full up in the window.
And, most the obvious place to mobilize is more like 600 feet down range at Hacienda and E Reno.
And, if a person in the hotel room below is standing in the window when incoming rounds start hitting the hotel, then too bad for him.