Yea, that’s plenty of time to get someone to investigate odd behavior. Obviously hindsight is 20/20, but you see stuff like that, have an officer go investigate and continue to keep an eye on the person. And yes, I get it’s easy for me to say that now we know what happened, but it would be a reasonable response.
Also, I know an officer did go up there and got a rifle pointed at him, but the situation should have been handled then, not after things went sideways. By either that officer or the counter sniper watching, who should have been keeping an eye on the situation.