Seger, who described his late pal as a "joy to be around" told the outlet that the "Hotel California" hitmaker had suffered from colitis most of his life, but had kept the effects largely under control thanks to an active workout regimen.
However, when the guitarist's health took a turn for the worse in November, he was induced into a coma by his doctors in New York.
"First he caught one set of pneumonia, then he caught a very virulent set of pneumonia," Seger explained. "They were trying like hell to keep him alive. He'd been at Columbia Medical Center since November," he went on.
"[Eagles manager] Irving [Azoff] pulled every ace out of the hole," Seger continued. "He had the eight best specialists working on Glenn. About a month ago, they had to throw up their hands.”
Azoff also spoke out on Monday about his devastation at losing Frey, declaring himself "heartbroken" to Billboard magazine. He described his late friend as "a great father and a great humanitarian who cared.”
"He loved his family," Seger added of Frey, who is survived by his wife, Cindy Frey, a daughter and two sons. "He loved those kids. He was devoted to them. He was so much more than people knew he was."
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