Doucette, who was born in Minnesota, grew up in Montana and Washington state. He attended the University of Washington, graduated with a law degree from Willamette University in Salem, Ore., and joined the FBI in 1983 at age 26.
An uncle had been in the FBI, and it was the only career that interested Doucette. He was especially drawn to intelligence work.
His first assignment was in the Sacramento field office, where he met Suzane, a divorced agent with two young daughters. In just over a year, they were married.
They were transferred first to New York and then to Phoenix. Suzane quit the FBI in 1993 after settling a sexual harassment lawsuit against the bureau. Brad's career, meanwhile, was on a steady climb.
By the time the Doucettes arrived in Los Angeles in 1994, he had worked almost all the prestige assignments: drug smuggling, bank robbery, white-collar crime. Then he moved into counter-terrorism.
Part detective work, part divination, the job requires agents and analysts to interpret wisps of information -- a telephone intercept in Pakistan, a suspicious passenger on a Paris-New York flight, a paid informant's tip -- to see if they foretell an attack.
Doucette seemed to thrive in the assignment. He worked on the investigation of the 1993 World Trade Center bombing, which killed six people and injured more than 1,000. The bureau's detective work laid the foundation for the conviction of four Islamic militants.
Doucette also helped supervise the investigation of the 1999 crash of an EgyptAir jet, which plunged into the ocean off New England, killing all 217 people aboard. The disaster was ultimately blamed on the copilot, who investigators said deliberately put the aircraft into a dive.
In 2000, Doucette ran the FBI command post for the Democratic National Convention in Los Angeles.
Even before Sept. 11, he wrestled constantly with how to chase an endless stream of leads. He worried that he might miss something, or pursue the wrong case, or act too late to prevent an attack.
"If he had a fault, it was that he cared too much," Moore said. "When you are a paramedic and see people die, you shouldn't dwell on their death and the loss. It's called building walls."
Doucette "couldn't build those walls," Moore said.
After Sept. 11, the atmosphere throughout the bureau became taut. Moore was one of three agents who helped Doucette pore over a stack of investigative leads every morning.
"It took four of us just to get through that stack every day by noon," Moore said.
While agents worked round-the-clock to prevent new attacks, the FBI was bombarded with criticism for having failed to detect the Sept. 11 plot.
It emerged that an agent in Phoenix, two months before the suicide hijackings, had alerted superiors that Muslim extremists were training at U.S. flight schools.
In August 2001, agents in Minnesota detained a French-Moroccan flight student who they suspected was training for a terrorist mission. The agents could not get clearance from FBI higher-ups to search Zacarias Moussaoui's laptop computer.
Moussaoui was in federal custody when the terrorists struck. According to the Sept. 11 commission, he had been preparing to participate in the hijackings or in a second wave of attacks that never materialized. Last month, he pleaded guilty to conspiring with Al Qaeda and faces the death penalty.
The FBI's Los Angeles office figured in another missed opportunity. In late August 2001, the CIA told the bureau that two suspected terrorists -- Nawaf al Hazmi and Khalid al Mihdhar -- were in the U.S. On Sept. 10, agents in New York passed the tip to Los Angeles, believing the men were in Southern California.
By then, it was too late. Hazmi and Mihdhar had left for the East Coast to participate in the hijackings.
The episode underscored how costly even the slightest lapse in vigilance could be.
"Brad shared everybody's concern: Did we somehow screw up?" Moore said.
Despite the pressure, Doucette found time for family, friends and football. A high school quarterback, he was a devoted fan of his alma mater, the University of Washington.
"He never missed a Huskies game" on television, Suzane said.
The couple lived comfortably in one of the Spanish-style houses that blanketed the suburb of Calabasas. Their next-door neighbors were Scott and Victoria Sterlekar.
"I'm sure, with the job he had, he was very serious at work," Victoria recalled. "But at home, he was really fun."
Suzane said her husband never let the stress get the best of him. Years earlier, they'd had occasion to discuss suicide when an agent in Los Angeles killed himself after being charged with public drunkenness and assault.
"We both agreed that suicide is never an option," Suzane recalled, "that no job is worth it."
Doucette had never given much thought to working at FBI headquarters. But in early 2002, he heard Mueller tell supervisors that the fight against terrorism required more talent and commitment than ever.