The Army psychiatrist who killed 13 people at Fort Hood is allegedly asking to join the Islamic State of Iraq and the Levant -- from his federal prison cell.

Nidal Hasan's attorney says the convicted mass murderer recently wrote a letter to ISIL leaders asking o become a citizen.

Hasan is on death row at Fort Leavenworth in Kansas after he was sentenced to death for the shooting rampage at Fort hood.

Officials say Hasan targeted unarmed soldiers who were preparing to deploy to Afghanistan and soldiers who were just returning from duty.

More than 30 people were injured in Hasan's attack, and 13 people were killed.

During his trial, Hasan claimed he objected to American military involvement against Muslims in Iraq and Afghanistan.