The U.S. military is confirming that a former Guantanamo detainee from Kuwait carried out a recent suicide attack in northern Iraq.

A spokesman for U.S. military’s Central Command told The Associated Press on Wednesday that Abdallah Salih al-Ajmi took part in an attack in Mosul.

U.S. Navy Cmdr. Scott Rye says authorities don’t know the motive for the attack, which was reported last week by Dubai-based Al-Arabiya television. Iraqi security forces were apparently targeted.

The U.S. transferred al-Ajmi to Kuwaiti custody from Guantanamo in 2005. A Kuwaiti court later acquitted him of terrorism charges.