AUSTIN -- State troopers are now forbidden to shoot from aircraft unless they are under fire, the Department of Public Safety said Thursday.In October, a trooper in a helicopter fired on a pickup being pursued by game wardens near the U.S.-Mexico border, killing two Guatemalan immigrants.DPS Director Steve McCraw announced the policy change while facing questions from lawmakers about the pursuit.Troopers mistakenly thought the truck was carrying a load of drugs, and the DPS has said the trooper opened fire to disable the vehicle. McCraw continued to defend that shooting, even while rolling out rules that would now forbid it.According to the revised policy, "a firearms discharge from an aircraft is authorized only when an officer reasonably believes that the suspect has used or is about to use deadly force by use of a deadly weapon against the air crew, ground officers or innocent third parties."A suspect driving aggressively or recklessly does not constitute use of a deadly weapon, the new policy states.The American Civil Liberties Union quickly applauded the move."We are relieved that Texas is ending this extreme practice, which no other Southwestern border states have ever allowed," said Terri Burke, executive director of the ACLU of Texas."We hope that this decision is a step, if only a small one, toward ending the culture of violence that pervades enforcement of border security in Texas."Criminal prosecutors in Hidalgo County are still investigating the shooting, which caused the truck to crash into a ditch.