How to get "Sniper Assassin" on Colorado?

[Colonel Vance]

Hello all, I'm asking here because I'm starting to feel stupid.
So, I'm playing the first campaign trying to get all challenges I left behind - problem comes when I get to Colorado, Sniper Assassin.

I tried killing everyone from the old water tower, seemed a good way to get some easy kills. Nothing. Either everyone starts shooting at me while I get away (so not while I'm shooting at the targets, for what I know nobody noticed me) or the challenge simply does not unlock when I leave. Very important: I was not recorded by any camera at any point.

I even tried a different thing earlier: I brought a sniper rifle with me and did the entire mission Suit Only, knocking out the targets and then killing them with the rifle.
I even got the Silent Assassin, Suit Only challenge with that run, but the Sniper Assassin one seems not to unlock.

Is there any particular issue on Colorado that you know of? Or anything that might be preventing me to achieve this challenge?

EDIT: I just noticed that by simply killing Ezra Berg on this map and then leaving the tower, as soon as the guards enter "Lockdown" mode, they all immediately start shooting at me, even if I'm wearing a disguise.

[Myrmuz [IRL]]

there are issues in this game with recognizing when you've actually completed challenges. there doesn't seem to be any fix atm, it's just luck if the game acknowledges what you've done.
the way the AI responds to sniping is very obnoxious as well. not much you can do about it other than get out of line of sight immediately after taking a shot and then leaving the area because they always seem to know exactly where the shot came from regardless of distance or sound.

[samDLIVE]

I recommend finding a way to knock out targets than safely sniping them at close range, also don't use the ghost variation of the sniper rifle, I've had issues with it sometimes not registering as a sniper kill, don't have this issue with any other sniper rifle. I agree wtih above poster though, they kinda ♥♥♥♥♥♥ sniping in this game, aside from the challenges, theres literally no reason to actually try to set up a creative sniping situation, because the ai logic is stupid vs sniper rifles.

[Kwama57]

I remember i cleaned the guards below and hid their bodies in available nearby crates, leaving a spot to hide for 47 in the one under the water tower just down the ladder. also knocked and hid the guards inside and near the batiment below, then shot targets until alarm went off to the next... Tedious but was efficient.

Looking back, as sniper challenge allow disguises i would just get the briefcase + rifle and shoot them close when isolated.

[Colonel Vance]

Originally posted by samDLIVE:

I recommend finding a way to knock out targets than safely sniping them at close range

Unfortunately I tried this already, but it did not work. As I mentioned in the thread opening, this unlocked Silent Assassin, Suit Only but not Sniper Assassin

[Mr_Faorry]

You don't need to do it suit only.

The way sniping worked changed this game, if you shoot someone nearby guards will be able to figure out where the shot came from and will lay down suppressing fire while moving in.
It's important to note that during this guards have no spotted you, you aren't compromised, they are simply alerted and will swarm the general area you shot from. If you get out of there before they can get there you won't be spotted and will still get the 'never spotted' bonus.

If you're interested in being told how to do it here is how I did it:

I started in the default area and brought a sniper.
Walked into the scrapyard and knocked out the two guards near the generator, from there I pulled out the sniper and waited until Rose and Pavati came into view and shot them (Pavati is only in view for a couple of seconds).
From there I instantly legged it to the orchard and then down to the tool shed where Beg sometimes and shot him through the fence as he walked past the lawnmower (with the timing he was walking away from the shed when I got there).
Then I went into the house and upstairs where I printed the mask and then out onto the balcony and shot Graves before heading down into the storm bunker and exiting.