The death of Border Patrol Agent Nicholas Ivie in New Mexico earlier this week appears to be the result of a tragic accident. According to NBC News' Pete Williams, investigators have concluded that Ivie was likely killed by friendly accidental fire by another agent while responding to a ground motion sensor alarm set off near the Mexican border. The chaotic incident involved two other agents who were patrolling on foot with Ivie about five miles north of the international border : One of them was hospitalized, the other left unscathed. 

As we noted earlier today, state and federal officials initially attributed the attack to armed criminals  shooting both agents—accusations that led Mexican authorities to arrest  two people as suspects in the case. Now it seems that the two agents simply shot each other. Still, as The Washington Post notes, more details are likely forthcoming. "The circumstances surrounding the friendly fire incident remain unclear, said the officials, speaking on condition of anonymity because the investigation is ongoing."