at one point arkady became very close with the two men. to his shame, arkady admitted to us after our interview that he himself did go along twice and struck captives. but now arkady has fled iraq, breaking out his graphic video, his family in hiding after receiving death threats from the two soldiers he once considered friends. do you think they would kill you? >> yeah, why not? it's easy. >> would you ever be able to go back to iraq? >> i don't know. really, i don't know. >> reporter: of all the images ar arkady showed us, the most disturbing may be one the soldiers themselves recorded on a phone and sent to him. it shows two soldiers chasing down a handcuffed prisoner and then carrying out a brutal field execution. >> that's extra judicial killing. i don't even have words for it. >> that's a murder? >> that's a murder. >> reporter: in our phone call, captain nazar told us human rights don't apply to people that he suspects of being isis. >>. >> translator: he's not human, he's a monster. >> isn't that murder? >> translator: no, it's not

. >> reporter: these dramatic battlefield pictures were made by an iraqi photojournalist, ali arkady, expecting to document the heroics of iraqi soldiers, working with the u.s. against isis. >> they are against isis and they are very strong. >> reporter: but arkady says he soon came to learn the soldiers he was embedded with for months, from what's called the emergency response division, were no heroes. and tonight, he is revealing the graphic images, licensed by abc news, that he captured of these important u.s. allies carrying out the torture and murder of civilians, only some of which is suitable for broadcast. was this happening all the time? >> this is happening all the time. >> reporter: this man, he says, was a sheep herder, whose teenage sons were suspected of working for isis. >> there's not even a pretext here of torture in the name of obtaining intelligence. this is just torture for fun. >> reporter: sadistic? >> sadistic. >> reporter: in a remarkable phone call with us, the unit captain, omar nazar, admitted the video was real and said he was proud of what was on the tape.