The distances they're likely dealing with are very likely a significant factor. Being that far away, optics can only do so much to show you what is happening.

It's hard to tell if it's a rifle or not, and if the rifle is a real gun or something like Airsoft or a pellet gun or something that doesn't actually pose any threat.

With the distance (or even up close) you can't really be picky about where you're aiming, you're just trying to hit something, so shots are generally towards the chest where you're most likely to hit, unfortunately shooting someone in the chest has the largest chance to be fatal, so you basically have to shoot to kill.

Killing someone for holding what looks like, but cannot be confirmed as a gun, on a building that's outside of your protection zone, is a tough call. Once a shot rings out, the intention of the person and what they have is made very clear, and taking a shot at that point is valid and warranted.

First, I don't think that SS, or any agency, wants to end the life of someone who is not doing anything wrong and not posing a risk to anyone, so IMO, they all rightfully err on the side of caution until a threat is confirmed or very obvious.

I'm aware that the local PD confirmed the threat, but I would assume that due to bad/slow/complex inter-agency and inter-team communication, the message did not reach the sharpshooter team which ultimately took the guy out... At least it didn't reach them prior to when the shots were fired.

Knowing what I do about radio, communications and the methods by which information is transferred, the local PD officer likely radioed dispatch about it, where they faffed about trying to find how to contact the SS, ultimately they probably called someone in the SS, who relayed it to an on-site (or dispatch type) operator, likely sending it out on the wrong channel (sharp shooters are often on their own channel AFAIK), and it took so long for the information to reach the sharpshooter team that by the time they could have set up the shot, he was already firing at Trump. This is all conjecture and speculation based on my experience running communications for various events (I'm not security nor medical nor anything else, I'm part of a team brought in specifically to relay information between locations in real time). There's often a bit of a game of telephone happening, and the message is usually not clear getting to the final person.

In my experience I've had bad reports from random event goers that turn into nothing. Recently at an event I had a report of someone collapsed, vomiting, and needing medical. When I arrived, there was nobody there, myself and the medical staff were thoroughly confused. We asked around and apparently, they didn't collapse, they threw up a bit (probably alcohol related as there was alcohol at the event), then shuffled off by friends. We had no description of the person, nothing to go on at all on order to find them and confirm their condition, only a vague direction from the witnesses in trucks and tents nearby. We never found them, and the person who originally reported it disappeared into the crowd as quickly as they appeared. So we were left to wander around trying to find someone who looked like they had just thrown up in a crowd of people (likely around 200 or more). Another example was someone saying there was an injury, gave a location and myself and the medical team jumped into action. We went to the described location and nobody needed help nor had an inquiry. After canvassing around for about 3-4 minutes, we found them several hundred feet away, stationary, waiting for us to arrive, but in a completely different area.

My point is, getting accurate information across from those that need help to those that can help is a challenge because the simple game of telephone between the points is unreliable at best. If you're ever reporting anything, to anyone, please, for the love of everything, be specific and direct. Don't just point and say, "over there" because there's an entire world of stuff "over there". If you can cite a nearby address or landmark, do that, otherwise give a direction and your best estimate of distance. If it's a person or thing, do your best to describe the individual or object. Don't assume that the recipient knows anything about the area.

I love doing communications work for events, it's one of my favorite hobbies. However, people are garbage at telling me what they need and where. To be clear, my team often works with medical/security, and often we travel with them to give updates to the rest of the team as we go. We have people listening where their only job is to relay information and record it, similar to dispatch. So we put as much information as we can on the air. Radio calls travel at the speed of light, so we can often get information distributed more quickly than having to pick up your cellphone and calling someone. Our systems are also independent from the cellphone networks so if there's a problem with those services, we can still operate, giving us an advantage over other options, including stuff like GMRS/FRS which can be intercepted or interfered with by anyone with a handheld radio capable of using those channels. I know that the police, military, secret service, Airforce, etc, all have their own, independent, radio frequencies that do not overlap, so communication between agencies is usually dealt with separately from the radio. The best case is that one member of an agency is outfitted with a radio from the other service, so dispatch can call them directly to relay traffic. Behind that is that two dispatch operators are in constant communication, either by phone or by presence (being physically near eachother), but neither seems to be the case here. No matter what, it's still a game of telephone to get a message from one agency to another, or even from one field operator to another when they're on different channels, even within the same service/agency.