Adel Daoud was sentenced Monday to 16 years in prison for a decision he made at age 18 — when he pushed what he thought was a detonator that would set off a half-ton car bomb in the Loop.

The detonator was fake. Daoud, of Hillside, was caught up in an FBI sting; he was sitting in the front seat of a car next to an undercover FBI agent when he pushed the button on Sept. 14, 2012.

He was arrested later that day and spent more than six years jailed ahead of Monday’s sentencing hearing, time that will be credited toward his sentence. Daoud’s mother spent most of the hearing either with her head bowed or peering anxiously at U.S. District Judge Sharon Johnson Coleman, pressing a kerchief over her mouth. As the judge addressed Daoud’s conditions of supervised release, which will extend 45 years after his release, his mother smiled at her husband.

Prosecutors had argued last week for a sentence of 40 years in prison, and U.S. Attorney John Lausch told reporters in the Dirksen Federal Building lobby that he was disappointed with the sentence. Daoud also will serve concurrent sentences for two offenses he committed while jailed: attempting to hire someone to kill the informant who set him up in the bomb case and attacking another inmate with a sharpened toothbrush handle.

“This gives him a life. We can’t ask for anything more than that. This is a terrific result. This gives him his life back,” Daoud’s lawyer, Thomas Anthony Durkin said. “If the government had its way he would not have a life.”

Judge Coleman, who noted that the hearing was held at the start of the Muslim holy season of Ramadan, as well as Mental Health Month, seemed to agree with the defense portrait of Daoud as a socially awkward, impressionable teenager at the time he encountered an FBI agent posing as a terrorist. The judge noted Daoud’s “high-pitched giggle” in taped conversations with the agent, and the fact the teenager used words like “fudge” and “mothercracker” in place of profanities.

“There is little doubt that, objectively, (Daoud) was an immature young man … he wanted to talk about politics or religion with a friend,” the judge said. “He did what teenage boys did, which is talk big and ‘woof.'”

But federal prosecutors say Daoud set out to commit mass murder in 2012 using a bomb that reeked of gasoline and was filled with wiring and “bags and bags of fertilizer” — a phony bomb built by the FBI. Prosecutor Barry Jonas said the realistic device should have scared the teenager. Instead, Daoud got excited.

“He believed he was fulfilling his mission for God,” Jonas had insisted last week.

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At the end of a three-day sentencing hearing last week that played out like a miniature trial, Daoud apologized.

“Sometimes I laugh at my stupidity.” He added: “I don’t want to kill people or join a terrorist group.”

“It was never too late to back out from the plan until I pushed the button,” Daoud told the judge. “I didn’t realize that.”

Troubled by his lengthy ramblings on the internet, the FBI opened its investigation into Daoud in May 2012. That July, Daoud would cross paths with an undercover agent he believed to be the cousin of someone he had been chatting with online.

Daoud continued to espouse radical ideas in his conversations with the undercover agent, letting the tone of his voice rise and fall wildly and laughing often. He suggested several potential targets for an attack — including Woodfield Mall, an address on Navy Pier and bars and military offices. Judge Coleman noted that Daoud also proposed an attacking using flying cars outfitted with kitchen knives.

In the end, he chose to set off a car bomb at the Cactus Bar and Grill. The undercover agent warned him, “People are gonna die.”

Daoud replied: “Yeah, that’s the point. … It has to be at least a hundred people.”

After his arrest, Daoud would enlist a fellow inmate in an attempt to have the undercover agent killed. He used the code words “How is Uncle Mike doing” on a recorded jailhouse call to set the plan in motion. Then, in 2015, Daoud attacked another inmate who had taunted him with a drawing of the prophet Muhammad. The attack left the victim covered in blood.

Durkin said the case called for the FBI to turn Daoud over for mental health treatment, rather than criminal prosecution, noting that Daoud was found unfit to stand trial and was only restored to competency after months of treatment and medication at a federal facility.

Daoud will be required to continue his treatment while in prison, as well as a “countering violent extremism” program. Daoud will be barred from any communication with anyone planning a crime, and from talking to anyone overseas other than family members approved by probation officials.

“The plan is for you to get out and for you to be successful when you get out,” Coleman said.

Contributing: Jon Seidel