Telescopic Sight

The Telescopic Sight's proc is signaled by a reticule appearing around the soon to be dead enemy, and a loud gunshot that sounds similar to the Sniper's Steady Aim ability,

Trivia
The text "Spinning while firing is also a great way to lose your license" is a reference to the trend of "360 No-scoping" kill done in the Call of Duty series especially, where the player would use a Sniper Rifle, spin 360 Degrees and fire without looking down the scope, supposedly showing a large amount of skill and good reaction times when done accurately.