The United States sent Guantánamo’s youngest captive home to a prison in his native Canada on Saturday, ending the decade-long U.S. detention of the Muslim militant who grew from a teenager into adulthood at the Pentagon’s prison camps in Cuba.

In 2002, at age 15, Omar Khadr hurled a grenade in war-torn Afghanistan that killed an American soldier. He was captured and kept by U.S. forces ever since. Now 26, he’s home and could serve up to six more years in a Canadian prison. Or authorities could release him sooner. Canada considers him a juvenile offender who can apply for parole a year from now.

“He thinks he’s in a dream. He’s pinching himself,” said Toronto attorney John Norris, who spoke to Khadr soon after his arrival. “He never believed this day would come; he’s been betrayed so many times before.”

Khadr departed the base in Cuba before dawn Saturday, a secret transfer 10 days after a Canadian diplomat paid Khadr a visit on his 26th birthday. He landed at a Royal Canadian airbase in Ontario and was transferred to the Millhaven maximum security prison for what his lawyer described as an assessment of the most suitable place to serve out his sentence.

The case of Khadr — Guantánamo’s last Western captive — stirred debate in international law and human rights circles.

Because he was captured at such a young age, some called him a child soldier who was dropped off in the war zone by his father and deserving of rehabilitation not interrogation. Others called him the respected scion of an al Qaida family, nicknamed Canada’s First Family of Terror in news reports, and opposed his repatriation.

Psychiatrist Michael Welner, testifying at the Guantánamo war court for the prosecution and paid by the Pentagon, called Khadr a continuing danger who spent his time at the U.S. prison camps in Cuba “marinating in a community of hardened and belligerent radical Islamists.”

Khadr’s lawyers offered up tales of abusive treatment in U.S. custody. He’d been questioned in Afghanistan while emerging from surgical anesthesia, they argued. He was used as a “human mop” at Guantánamo after he urinated on himself and the floor during an interrogation. His lawyer was forbidden from seeing him during his first two years of interrogations.

U.S. troops captured Khadr, who was near death, in a July 27, 2002 firefight at a suspected al Qaida compound near Khost, Afghanistan.

U.S. air strikes had leveled the compound and as a Special Forces unit assaulted, Khadr admitted in a 2010 guilty plea, he threw a grenade from the rubble that mortally wounded Army Sgt. 1st Class Christopher Speer, 28. Medics were able to save Khadr’s life and turned him over to what became a decade of on-again off-again interrogation.

Since his conviction, he was confined to a maximum-security wing at Guantánamo, a mostly solitary existence that his lawyers tried to ameliorate with a Canadian-style college preparatory curriculum — literature, physics and videos of “Little Mosque on the Prairie,” a popular Canadian TV show about a Muslim community in a fictional prairie town.

He also read Shakespeare with his U.S. defense lawyer, Army Lt. Col. Jon Jackson, who played Juliet to Khadr’s Romeo.

“Now that Khadr is back in his own country, Canada should assist in his rehabilitation,” said Human Rights Watch counterterrorism counsel Andrea Prasow. “International law provides him the right as a former child soldier to be reintegrated into society.”