U.S. District Judge Miriam Cedarbaum refused to hear him read it Monday, instead challenging the Pakistan-born American citizen to just say "what happened."
In an unapologetic, matter-of-fact courtroom colloquy that followed, Shahzad offered chilling details about how he trained with the Pakistani Taliban to build bombs, then returned to the U.S. to launch an attack that would avenge attacks on Muslims by U.S. forces overseas.
"One has to understand where I'm coming from," he said in an unusual departure from tightly scripted guilty pleas, with his defense attorney and prosecutors sitting in silence in federal court in Manhattan. "I consider myself ... a Muslim soldier."
Shahzad, 30, admitted leaving an SUV rigged with a homemade bomb in bustling Times Squares on a warm night on May 1. The bomb failed to go off, and the Bridgeport, Conn., resident was arrested trying to leave the country on a Dubai-bound flight two days later.
Authorities say following his capture, Shahzad voluntarily started talking about the botched bombing right away - a pattern that continued in open court, where he agreed to plead guilty to 10 terrorism and weapons counts without the benefit of a plea deal and with certainty he'd face life in prison.
"I want to plead guilty, and I'm going to plead guilty 100 times over," he said.
Until U.S. forces leave Muslim territory, he added, "we will be attacking U.S."
Sentencing was set for Oct. 5, and prosecutors say that at least one of the counts to which Shahzad pleaded guilty carries a mandatory life term. With no parole in the federal system, that means he would die behind bars.
Widely circulated snapshots of Shahzad - a U.S.-trained financial analyst and married father of two - show him with a neatly trimmed beard, all smiles and looking carefree behind sunglasses driving a car, or standing next to his American wife.
When led into court on Monday, he had on a white skull cap and prisoner's uniform, his beard shaggy and his demeanor full of pride and absent remorse.
Shahzad traced his plot to a 2009 trip to Pakistan that began only three months after he received his U.S. citizenship.
While staying with his parents, he ventured into the lawless Waziristan region in December with "a couple of friends ... to join the (Pakistani) Taliban." He didn't describe the friends any further.
But an intelligence official in Pakistan told The Associated Press that CIA investigators have been given access to two Pakistani men who helped Shahzad reach Mir Ali town in North Waziristan, as well as to three other suspects being held by Pakistani authorities. The official insisted on anonymity because Pakistan's intelligence agency does not allow its operatives to be identified.
Shahzad said he sought and received five days' training in explosives before returning to the United States in February to pursue a one-man scheme to bring death and destruction to New York with funding from the militant group. The indictment said he received $5,000 in cash on Feb. 25 from an unnamed coconspirator in Pakistan and $7,000 more on April 10, sent at the coconspirator's direction.
He explained that he loaded his vehicle with three bomb components, hoping to set off a fertilizer-fueled bomb packed in a gun cabinet, a set of propane tanks and gas canisters rigged with fireworks to explode into a fireball. He also revealed he was carrying a folding assault rifle in a laptop computer case for "self-defense."
Shahzad said he expected the bomb to begin going off after he lighted a fuse and waited between 2½ and five minutes for it to erupt.
"I was waiting to hear a sound, but I couldn't hear any sound...So I just walked to Grand Central (Terminal), and I went home," he said.
Authorities say the bomb malfunctioned, emitting smoke that attracted the attention of an alert street vendor, who notified police, setting in motion a rapid evacuation of blocks of a city still healing from the shock of the Sept. 11, 2001, terrorist attack on the World Trade Center. At a minimum, police said, the explosive had potential to harm nearby pedestrians and damage buildings with flames and shrapnel.
The judge kept up a steady back-and-forth with Shahzad, questioning how it was possible he pulled off the near-bombing solo.
"You built the bomb all by yourself?" she asked.
"Yes. ... Nobody helped me," he replied.
She also pressed him on how he could target U.S. civilians if his goal was to retaliate against U.S. forces, asking of the potential in Times Square that night, "Did you look around to see who they were?"
"Well, the people select the government," Shahzad said. "We consider them all the same. The drones, when they hit ..."
Cedarbaum interrupted again: "Including the children?"
Shahzad answered: "Well, the drone hits in Afghanistan and Iraq, they don't see children, they don't see anybody. They kill women, children, they kill everybody. It's a war, and in war, they kill people. They're killing all Muslims."
Later, he added: "I am part of the answer to the U.S. terrorizing the Muslim nations and the Muslim people. And, on behalf of that, I'm avenging the attack. Living in the United States, Americans only care about their own people, but they don't care about the people elsewhere in the world when they die."
Attorney General Eric Holder said after the plea: "Faisal Shahzad plotted and launched an attack that could have led to serious loss of life, and today the American criminal justice system ensured that he will pay the price for his actions."
Pakistan has arrested at least 11 people since the attempted attack; none have been officially charged. The father of one of the men detained said he has submitted a court petition for information about his son, Salman Ashraf Khan, but received nothing.
"If somebody is dead, the mourning period lasts 40 days," said Rana Ashraf Khan. "But this is the 43rd day my son is missing."
Three men in Massachusetts and Maine suspected of supplying money to Shahzad have been detained on immigration charges; one was recently transferred to New York.
Federal authorities have said they believe money was channeled through an underground money transfer network known as hawala, but they have said they doubt anyone in the U.S. who provided money knew what it was for.