The likelihood they didn't know where he was, they heard the report from the shooter, almost immediately zeroed in on his position, lined up the shoot and eliminated him that quickly is highly improbable.
In wide open spaces you can't hear a gun shot then almost instantly know it's exact origin. You can hear a shot from one direction and have a vauge idea of a 90 degree area it came from like left, right, behind you and so on. But the chances they heard the report and immediately found the source requires happening to be the first place you look is the exact spot. Especially if there is a surface sound direction can be altered from like a structure that can redirect sound, or something that can deden sound.
So is it impossible? No but it's really really damned unlikely they found him and eliminated him that quickly based entirely on a rifle report.
But then again, I don't know what kind of equipment they have now. My experiences come from decades ago.