PHOENIX – The shooting of two U.S. Border Patrol agents near the Arizona-Mexico border may have been a case of friendly fire, a union chief for border agents and law enforcement officials said Friday.

The development could shake up the investigation into the death of one of the agents that reignited the political debate over security on the border.

George McCubbin, president of the National Border Patrol Council, a union representing about 17,000 border agents, said Friday that he has learned new details that make him believe friendly fire could have played a part in the shooting.