Could be either way, but firing into a group of 100 people because one of them is a legitimate target isn't a safe procedure. From the story, it sounds as if the shooter got his intended target. Who got the other two victims is still unknown, but the article I posted has a security firing in the direction where two of the wounded were found.
The way I picture it, I see a balcony where when shots are fired, everyone either started moving away from the guy shooting, or got down. If the shooter was still shooting, then there was a clear target to shoot at.
Which is safer, trying to take him out, or letting the guy continue shooting (especially if you have no idea if he is after one target or many)?
If a guard had a shot, I think he had to take it.