American Who Joined Rebels to Fight ISIS in Syria Killed

— -- Levi Shirley, a 24-year-old American who volunteered to join forces with a Kurdish rebel group to fight ISIS inside Syria, died in combat earlier this month, his mother said today.

"I'm basically in shock right now," Susan Shirley told ABC News after learning from American officials and a rebel commander that her son was killed in combat. Levi joined the Kurdish rebel group known as the YPG, which also announced Levi's death today on it's Facebook page.

Levi Shirley died on July 14 in the heavily contested Syrian town of Manbij, according to the rebel group. The Facebook posting includes a video where Levi – calling himself Jack – speaks about why he went to fight ISIS. “They’re my definition of pure evil," Shirley said. "I don’t think good people in a society can stick other people inside of a cage and set them on fire, so yeah I came here to stop them."

His mother says Levi left in January of this year, telling her he was going to Texas to go to school and learn to become an Emergency Medical Technician. "He would have been an ideal EMT," Susan said. But soon Levi became evasive and fell out of touch. She wasn't entirely sure of where he was until she learned of his death this week. His mother said Levi had fought in Syria last year, but that he had come home after that.

"He knew going back that second time he knew what he was up against," Susan said. "He knew, he didn't have any illusions that war is romantic. When he came back the first time, in fact, he said I am never fighting again."

The U.S. State Department discourages Americans from joining forces with rebel groups such as the YPG. State Department spokesman John Kirby would not publicly discuss the matter, citing privacy concerns. He said only that the State Department was aware of reports that an American was killed inside Syria earlier this month while fighting alongside Kurdish militants.

Shirley is not the first American to fight and die with an unconventional force inside Syria. American Kieth Broomfield died just over a year ago fighting with the same group.

"Even from a tiny kid, he had a big heart," Susan Shirley said today. "He has a very strong instinct for defending people. As much as I would have preferred he didn't go back that second time, I do get why he did."