In advance of the court date, prosecutors filed new details with the court.
ABC15 has learned Terry and the other agents with him were just finishing up a 48 hour mission near the Arizona-Mexico border. They were looking for a group of so-called border bandits who had been operating in the area for about a year. The men were suspected of theft and murder.
The agents had just an hour to go when the battle that would end Terry's life began. According to other agents there that day, a group of five men showed up, guns drawn. Agents yelled out, "Police, police, policia!" That's when court records say the bad guys started shooting.
Agent Terry was shot and shouted out, "I'm hit, I'm hit! I can't feel my legs." Moments later, he lost consciousness and died.
On Monday, Manuel Osorio Arellanes will be sentenced. He faces up to 30 years in prison after pleading guilty to first degree murder.