When he was seven, Rubenis's parents Mort and Nadine were both killed in a car accident. Morgan also deduced from Rubenis's sniping skills that he was ex-military. At some point, he became a hitman and a member of a network of hitmen that cropped up after the dismantlement of the Silk Road by the FBI in 2013.
Though he doesn't physically appear in the episode, Rubenis manages to give a prison guard a toxic substance, which is used to kill fellow colleague Giuseppe Montolo. After the guard is successful in poisoning Montolo, Rubenis kills him in order to remove loose ends.
Off-screen, he was hired by NSA Director Brian Cochran to kill Bernard Graff, who was investigating the Libertad Cartel, a drug cartel Cochran was running. When Graff sets up a meeting with Hotch and enters his car, he is shot in the head by Rubenis, who then makes it look like a suicide.
Rubenis is seen watching over Barry Winslow, the group's hostage and technical analyst, at the network's safe house. As he readies his artillery, Barry Plyman enters the house with his own supplies. Just then, SWAT agents storm the house, led by the BAU. Rubenis grabs a handgun and tries to shoot Rossi, JJ, and a SWAT agent with it, but JJ kills him before he could pull the trigger.
Rubenis would kill his victims from a maximum distance of 2,000 meters by shooting them with a Remington 700 AICS sniper rifle, hence his nickname. It is likely that he would be contacted and paid by his clients with each contract kill. When he had Montolo killed, he paid a prison guard to poison him to prevent him giving any information he knew about the network to the BAU. In the case of Bernard Graff, he used his gun to shoot him and made it appear as if he committed suicide.
No official profile of Rubenis was made by the BAU, since they focused on the network as a whole, although Morgan did believe he was ex-military, if not in the U.S. then in another country.
- Killed numerous unnamed victims prior to Entropy
- Unspecified date and location: One or two unnamed men (hired by an unnamed client to carry out the hit; shot)
- 2015, U.S.:
- December 2015-January 2016, unspecified location in the U.S.: Attempted to shoot the following:
- Though Rubenis's true name and personal background were never revealed in Entropy, they could be seen on a spreadsheet the BAU made of the network and a group of operatives-for-hire that abducted Morgan in Derek. This spreadsheet was seen in The Sandman and A Beautiful Disaster, and the show's Twitter account also released a photo of the prop in one of its posts while promoting the latter episode.
- Mark Semos, the actor who portrays Rubenis, previously appeared on Criminal Minds, portraying a SWAT agent in the Season Ten episode Lockdown and an FPS leader in the Season Eleven episode The Witness. He has also done some occasional stunt work for the series since Season Six.