It was about 9:20 a.m. when FBI agent Rick Mains, helping to serve a fugitive arrest warrant in Washington, D.C., heard the alarming call on his bureau radio: The Pentagon had been rocked by an explosion.
What began as a routine day Sept. 11, 2001, turned quickly into a swirl of chaos and terror, one that would alter the course of his career, along with those of thousands of other FBI agents.
He was ordered back to his field office, a short walk north of the U.S. Capitol. His team, with every member fully accounted for, was quickly briefed on what would become a life-changing assignment.
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The explosion, they learned, was American Airlines Flight 77, overtaken by terrorists and flown directly into the side of the Pentagon building across the Potomac River.
As smoke billowed and sirens wailed, there was time only to don protective gear and react.
"I never thought that something like that would happen in the United States," said Mains, who will be keynote speaker at Tuesday's Patriot Day Remembrance in Worthington, marking the 17th anniversary of the terrorist attacks that killed almost 3,000 people and injured more than 6,000 others in New York City, Washington and Shanksville, Pennsylvania.
Within an hour, he would be among the first to enter the wreckage at the Pentagon.
Mains, a Westerville native, is the assistant special agent in charge of anti-terrorism for the southern half of Ohio. Like others in his profession, he downplays his 9/11 role. Yet he realizes that personal stories help to honor the victims and reinforce a nation's resolve.
"I was one of the many agents to respond to the attack on the Pentagon," he said. "There was a great sense of duty to take care of the injured ... to get anyone out who was still alive. There was a sense of gravity we felt, by everybody."
Outside, the massive gaping hole in the iconic building exposed fully intact offices, sheered of their exterior walls. In one, a military and U.S. flag were standing. The occupant survived. The flags were retrieved, folded and presented to the victim by military personnel at a local hospital, Mains recalled.
Mains and his colleagues took no photographs out of respect for the dead and injured. Memories, though, are his personal, sometimes troubling, record.
"I witnessed things that I never thought I'd ever witness in the FBI," he said.
He paused, remembering an office cubicle, fully intact, but surrounded by rubble.
"On the desk of this cubicle was a picture of this individual family ... on this desk, it was untouched. The picture was upright and undisturbed.
"I knew that somebody was not going home to their family that night."
It was a 14-hour day of search and recovery amid jet fuel and pulverized stone. His work boots were burned from the embers and heat inside.
It would be followed by two months of dust, shovels and wheelbarrows, searching for evidence to help identify victims, including civilians aboard Flight 77.
His job, and the FBI's priority, instantly shifted to preventing future terrorist attacks. He volunteered to go to Afghanistan, embedded with Special Operations forces, and in direct combat, during several four-month assignments.
Mains was eager to return to Columbus about two years ago. Here, he's continued to investigate terror plots, including early work on Demetrius Pitts, who was charged with planning a July 4 terror attack in Cleveland.
Fellow agent Tom O'Connor, president of the FBI Agents Association, worked with Mains and has kept in touch with him.
"I think anyone who works a 9/11 site will have a bond," O'Connor said. "It was horrendous working conditions. But with guys like Ricky, there were no complaints. He just soldiered on and continued to do the job he was asked to do."
Mains, 51, remains comforted that the agency, working together with all levels of law enforcement, has made a difference in the country's safety.
"I'm very optimistic," he said." The federal government's ability to respond to any threat is robust. The threat is ever-changing, but so are we."