A former U.S. Army sergeant pleaded guilty in a New York court Friday to charges that he conspired to murder an agent of the Drug Enforcement Administration (DEA) and an informant, after being snared in an elaborate sting operation by authorities.

Joseph Hunter, 49, who was a sniper instructor, recruited an international team of former military personnel, many of whom were also snipers, to work as security and enforcers for what they believed was a Colombian drug cartel.

In fact, his employers were working in cooperation with the DEA. Hunter and five other men were arrested in Sept. 2013, after being recorded agreeing to kill a DEA agent and an informant in Liberia for $800,000, the BBC reported. The murders never took place.

Three of the other men arrested with Hunter, former U.S. Army Sergeant Timothy Vamvakias, former German sniper Dennis Gogel and former Polish sniper Slawomir Soborski, have already pleaded guilty to charges associated with the plot and are awaiting sentencing. The fifth man charged in the case, former German military sniper Michael Filter, goes on trial in June, according to Sky News.

Hunter's lawyers unsuccessfully sought to have the charges against him dismissed on grounds of outrageous government conduct, the New York Times reported. They cited the DEA’s use of a cooperating witness -- a former boss of Hunter’s who had threatened to kill him in the past -- to introduce Hunter to the informers who were posing as traffickers.

One of the charges Hunter pleaded guilty to carries a ten-year minimum sentence, and he could face up to life in prison when sentenced in May. In addition to the conspiracy to murder charges, he pleaded guilty to conspiring to import cocaine into the U.S., and firearms charges.

Hunter’s lawyer, Marlon Kirton, told the New York Post that his client's “judgment was severely affected by his PTSD [Post Traumatic Stress Disorder],” and urged the sentencing judge to take it into consideration. Hunter was reportedly diagnosed with PTSD after serving in Iraq.

In a release cited by the Associated Press, U.S. Attorney Preet Bharara said Hunter became "a soldier of misfortune who recruited and led an international band of criminal mercenaries. This global gun for hire will now be confined stateside in federal prison."