ARIZONA – An Arizona teenager who the FBI said professed himself to be an “American jihadist” has agreed to plead guilty to terrorism and conspiracy charges stemming from a suspected plot to bomb a state motor vehicle office, court documents showed on Monday.

Mahin Khan, 18, jailed since his arrest in July, reached a deal with prosecutors in which they agreed to seek a prison term ranging from seven to 14 years, rather than the life term he potentially faced if tried and convicted.

Khan, who according to his parents suffers from autism and developmental delays that have left him with the mental age of a 12-year-old, is scheduled to return to court on Nov. 4 to formally enter his plea and be sentenced.

Under his plea deal, reached on Friday, Khan agreed to plead guilty to all three charges contained in the indictment against him – terrorism, conspiracy to commit terrorism and conspiracy to commit misconduct involving weapons.

According to the Federal Bureau of Investigation, the case stemmed from months of communications between the defendant and undercover FBI operatives in which Khan expressed a desire to carry out “lone jihadist” attacks that would kill hundreds of people in Arizona.

Khan ultimately set his sights on a Division of Motor Vehicles office in the Phoenix area, reasoning that relatively light security and crowded conditions there offered the best chance of inflicting high casualties, prosecutors said in court.

Prosecutors also said Khan, a resident of Tucson, sought to obtain weapons such as pipe bombs or pressure cooker bombs for the planned DMV attack in communications with an individual he believed was an Islamic State fighter.

In an affidavit filed in court, the FBI said Khan had described himself in an email as an “American jihadist” who supports Islamic State, the militant group that has seized parts of Syria and Iraq and claimed responsibility for deadly bomb and gun attacks in other countries.

But in a statement to local media in July, Khan’s parents said their son lacked “the mental capacity to carry out the horrendous acts he is accused of planning” and posed no danger to public safety. The parents also said their son previously underwent “extensive inpatient psychiatric evaluation under the directive and supervision of the FBI.”

The FBI has acknowledged that Mahin first came to the agency’s attention when he was 15, and that his family was urged to seek mental health treatment for the boy.