The soldier, Army 1st Lt. Michael Behenna, had captured the prisoner in a raid where an arms cache was also discovered. The prisoner was held by military intelligence in connection to a roadside bomb that had killed two soldiers. No evidence was found connecting the prisoner to the bomb, and he was ordered released. While returning the prisoner, Behenna claimed that he sought to question him further. He stripped the prisoner of his clothes and shot him.

Behenna was convicted of murder and sentenced to 25 years, and received parole after 5 in 2014. Trump’s pardon removes all prior restrictions from his parole.

NPR – Trump Pardons Michael Behenna, Former Soldier Convicted Of Killing Iraqi Prisoner
USA Today – ACLU blasts Trump’s pardon of soldier Michael Behenna as ‘endorsement of a murder’
Wikipedia – Michael Behenna