BETHLEHEM, Pa. (AP) — Sixteen thousand tons of Bethlehem Steel collapsed in a matter of seconds Sunday as a demolition crew imploded Martin Tower, the defunct steelmaker’s former world headquarters. Crowds gathered Sunday to watch the demolition of the area’s tallest building, a 21-story monolith that opened at the height of Bethlehem Steel’s power and profitability. America’s second-largest steelmaker went out of business in 2003.