(CNN) -- Guantanamo Bay detainee Omar Khadr pleaded guilty to charges against him Monday, the Pentagon said, in the first military commission trial there since Barack Obama became president. Khadr, 24, was accused of throwing a grenade during a 2002 firefight in Afghanistan that resulted in the death of Army Sgt. 1st Class Christopher Speer, a Special Forces medic. He also admitted that he "converted landmines to Improvised Explosive Devices and assisted in the planting of 10 IEDs with the intent of killing American forces" in the months before killing Speer, the Pentagon said. Khadr, the youngest detainee at Guantanamo Bay, was 15 at the time. He faced a maximum sentence of life in prison.
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NEW: Plea deal includes an eight-year prison sentence, source says
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Omar Khadr, 24, accused of throwing a grenade that killed a Special Forces medic in 2002
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Khadr was born in Canada, which held negotiations over his plea
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It's the first Guantanamo military commission of the Obama era
The military court in August viewed a 30-minute video that the government said shows Khadr helping to assemble and plant roadside bombs targeting American troops in @placeholder.