In recent weeks, no fewer than three Isil commanders in Sirte have been shot dead from long range, according to local media.
The killings are said to have sowed panic among Isil's forces in the city, who have carried a string of arrests and executions in a bid to track down the culprit.
The Sirte assassin's most recent casualty, according to social media reports from Sirte, was Abdullah Hamad Al-Ansari, an Isil commander from southern Libyan city of Obari, who was shot dead on January 23 as he left a city centre mosque.
The identity of the mystery marksman - if indeed it is just one - is now the subject of frenzied online discussion. Many believe he may be a militiaman from the neighbouring city of Misrata, whose security forces fought Isil for control of Sirte in the early part of last year but eventually pulled out.
The ticks are looking for a guy, when it could easily be a lady sniper.
It wouldn't be the first time the girls got into the act. After all, fine hand to eye coordination is critical to good sniping.
Adding to the sense of intrigue is speculation that the sniper might be a American special forces soldier, some of whom are thought to be operating in the region to gather intelligence on the Isil presence.
Here's your American sniper, ISIL!
I like it that the sand ticks are knocking each other off, but think it might be the work of an all powerful, super American sniper, a la Chris Kyle or Carlos Hathcock. If only. Obama would never authorize such a plan against his friends, but the ticks apparently don't realize that.