ISIS released a gruesome video online on Tuesday that appeared to show a young boy execute two suspected Russian spies.

According to reports from Fox News, the video showed the two victims being interrogated in Russian by ISIS soldiers. One prisoner, believed to be a Kazakh citizen, confessed that he was sent to spy on an ISIS leader while the other one admitted to his assignment to assassinate a senior ISIS commander.

The video later skips to the next scene where the spies are kneeling in an open field while a militant and a boy holding a pistol, who looked around 10 years old, stand behind the spies.

"Allah has gifted the Islamic State's security agency with the apprehension of these two spies," the man states. "By Allah's grace, they are now in the custody of the lion cubs of the Caliphate."

The young boy then steps forward, aims his gun, and shoots the two men from behind and one of them repeatedly. The young boy pumped his pistol in the air and smiled wildly after the killing, according to Fox News.

The video ends with a clip of previous propaganda from last November showing an ISIS camp where they are  apparently training child soldiers as future jihadis, which they call the "lion cubs of the Caliphate."

The same young boy appears in the video clip introducing himself as "Abdullah" from Kazakhstan. He spoke of his ambition to "kill infidels" when he grows up.

The US State Department did not give any comment, as well as the Russian Federal Security Service, and the Russian embassy when asked by news agency, RIA Novosti.

According to the recent study by the Middle East Media Research Institute, ISIS has been using children to participate in their military activities, but the video is the first graphic evidence of a child involved directly in the execution of prisoners, Fox News reports.