Sager had been hospitalized in a coma with severe brain trauma since the May 11 incident at Molly's Pub in Buffalo.
The bar manager, Jeffrey Basil, is currently charged with attempted murder, assault and tampering with evidence. The charges could be upgraded in light of Sager's death. Basil has pleaded not guilty.
Sager was a 28-year-old former crew chief with the Air National Guard and was engaged to be married. He spent three months in Afghanistan with the 107th Airlift Wing out of Niagara Falls
With Sager's death, this could lead to a murder charge against Basil.