Premise: In this Wednesday, Aug. 16, 2017 photo, a nurse attends to Argelia Mansio who was injured by a stray bullet during an assault staged by unknown attackers at the Roosevelt Hospital, in Guatemala City. The deputy hospital director told reporters that 12 people were wounded, including a child who underwent surgery and was in critical condition. Luis Soto AP Photo
Hypothesis: The stray bullet was fired by a former military firearm.