(CNN) -- This week's fatal shooting of a Border Patrol agent and the wounding of another was likely the result of friendly fire, the FBI said Friday. "While it is important to emphasize that the FBI's investigation is actively continuing, there are strong preliminary indications that the death of United States Border Patrol Agent Nicholas J. Ivie and the injury to a second agent was the result of an accidental shooting incident involving only the agents," said James Turgal, special agent in charge of the FBI's Phoenix division.