Hollywood actor Alex Baldwin did not have any reason to fire the gun that led to the fatal on-set shooting of cinematographer Halyna Hutchins on the set of “Rust” last month, a new lawsuit filed on Wednesday claims. Script supervisor Mamie Mitchell, who called emergency services after Baldwin shot Hutchins, filed the lawsuit (pdf) in Los Angeles County Superior Court, accusing the actor of having fired the gun without any valid reason to do so. “Alec Baldwin intentionally, without just cause or excuse, cocked and fired the loaded gun even though the upcoming scene to be filmed did not call for the cocking and firing of the firearm,” Mitchell said in the lawsuit. “Mr. Baldwin chose to play Russian Roulette with a loaded gun without checking it and without having the armorer do so.” “There was nothing in the script about the gun being discharged by defendant Baldwin or by any other person,” the lawsuit adds. Hutchins, 42, …