David Lawrence, a 20-year-old private first class, faced a military hearing yesterday at Fort Carson to determine whether he would stand trial for allegedly killing Mullah Mohebullah, a shackled detainee being held in a cell by the U.S. Army in Afghanistan. Lawrence is accused of premeditated murder in the October 17 incident, which Afghan President Hamid Karzi has called an “assassination,” writes The Denver Post.

But Lawrence said during his Article 32 military hearing that he had sought help for mental health problems and was taking Zoloft (a medication used to treat anxiety, depression, and other problems) the day he was assigned to guard Mohebullah, an alleged Taliban commander. Lawrence also said he only slept for a few hours in the days prior to the shooting. James Culp, Lawrence’s attorney, said he had “grave concerns” that his client is not mentally competent, asking for a delay and noting that Lawrence is taking the strongest possible dose of a medicine used to treat schizophrenia. Lawrence nodded off several times during the hearing, according to the Colorado Springs Gazette.

The case otherwise seems damning for Lawrence: “He said, ‘I killed him,'” staff sergeant Dominic Buscemi testified about the moments after the prisoner was shot. “I said, ‘Killed who?’ and he said, ‘The guy in the cell.'”