After more than 17 years behind bars, John Walker Lindh, the man who became known as “American Taliban” is now out of jail. He was sentenced to 20 years, but got out early due to good behavior. The Washington Post reports:

The Northern California native was captured months into the fight against the Taliban in Afghanistan, a war that has now lasted longer than his incarceration. The revelation that a young American had joined the group that harbored the 9/11 terrorists was a national shock.

Lindh pleaded guilty in 2002 to aiding the Taliban and carrying weapons. Prosecutors were unable to prove, however, that he went beyond fighting the Taliban’s Afghan enemies by aiding terrorists or trying to kill Americans.

NBC says his release comes “amid concerns among U.S. authorities that he remains a potentially violent Islamic extremist:”

Underscoring those worries is Lindh’s 2015 handwritten letter from prison to NBC’s Los Angeles station KNBC —revealed for the first time Wednesday — in which he expressed support for ISIS, saying the terror group that beheaded Americans was “doing a spectacular job.”

“The Islamic State is clearly very sincere and serious about fulfilling the long-neglected religious obligation to establish a caliphate through armed struggle, which is the only correct method,” Lindh wrote.

The family of Mike Spann has been lobbying against Lindh’s release. ABC reports Spann, a former CIA agent, interrogated Lindh after his arrest and was killed an hour later in a gun battle with militants. Though Lindh was never directly connected to the death his family has pleaded with Donald Trump to keep him behind bars.

NPR adds:

He’s getting three years off for good behavior, though his probation terms include a host of restrictions: He needs permission to go on the Internet; he’ll be closely monitored; he’s required to receive counseling; and he’s not allowed to travel.