Apparently surveillance officer didn't get a good look at him, he was busy relieving himself. He wasn't wearing a padded jacket - just a denim one. He didn't jump over the barier - even stopped to pick up a paper. All police officers were plain clothes - none of the witnesses heard a warning - that poor man didn't stand a chance.
I am not judging - in that climate i would not want to have to make the decision that the police officers had to - just sad at such a tragic waste of life - can't even begin to imagine what his family are going through now.