A former Lightning assistant is now at the helm as Dallas’ head coach, but it came about under odd circumstances.Dallas fired coach Jim Montgomery on Tuesday due to a “material act of unprofessionalism,” the term used by general manager Jim Nill. Rick Bowness has been promoted to interim head coach.Bowness was the Lightning assistant coach responsible for defense for five seasons. Jon Cooper hired him in June 2013, after Cooper’s partial first season in the NHL. The Lightning parted ways with him before last season.The 64-year-old Bowness has been head coach of five different NHL teams, but none since a 20-game interim stint with the Coyotes in 2004.Nill said Montgomery’s firing was separate from the four-point plan NHL commissioner Gary Bettman laid out on Monday concerning a code of conduct. He said there is no criminal investigation is underway and the incident does not involve current or former players.That separates whatever happened from the abuse allegations that have come out against hockey coaches at all levels after Calgary fired Bill Peters as head coach.Dallas is now the fourth team to fire a coach this season. Toronto and New Jersey also fired their coaches for the more common reason of losing too many games.