The 42-year-old gunman who tried to breach the FBI's Cincinnati field office Thursday before being fatally shot by authorities was a Navy veteran who had manned sensitive equipment aboard an attack submarine, according to his service record provided by the military.

Ricky W. Shiffer, whose identify was confirmed Friday by Ohio state police, served in the Navy for five years as a fire control technician aboard the nuclear-powered USS Columbia, according to his record.

Submarines are inherently sensitive assignments requiring extensive vetting, and Shiffer's job was particularly secretive. After enlisting in June 1998, he underwent 10 months of training before being assigned to the USS Columbia, where he oversaw electronic equipment associated with weapons such as missiles and torpedoes.

The Navy record did not list any individual awards for Shiffer. He left the service in 2003 as a noncommissioned officer.

Shiffer later served for three years in the Florida National Guard as an infantryman, said Catalina Carrasco, a spokesperson for the National Guard Bureau. He was honorably discharged in 2011.

Shiffer was shot by police after fleeing the FBI building and leading officers on a chase that led to a six-hour standoff on a rural road, the Ohio State Highway Patrol said in a news release. After negotiations failed, police attempted to utilize "less lethal tactics" to arrest Shiffer, but he "raised a firearm" and officers shot him, they said.

Shiffer died at the scene. Authorities are investigating a possible motive, in addition to Shiffer's possible ties to extremist groups, a law enforcement official familiar with the investigation said. His name is used on several social media platforms by an individual who spoke about being at the U.S. Capitol on Jan. 6, 2021, and urging a "call to arms" after the FBI executed a search warrant at former president Donald Trump's Florida estate on Monday.

Since the search, threats of violence against the FBI from Trump supporters online have increased, and Republicans have intensified criticism of the agency.

Shiffer was the oldest of four siblings and grew up on a farm in Perry County in Central Pennsylvania, near the Susquehanna River. His father worked as a farmer and diesel mechanic, and his mother as an insurance company employee, said a family member who did not want to give his name due to the sensitivity of the matter.

The relative remembered Shiffer as a "very intelligent but quiet person."

"He had quite a memory on him," the family member said. "It was full of facts and information when he would talk about something. He knew a lot about farm equipment."

The Shiffers had a small family farm with just a few animals - pigs and a cow - that they would occasionally butcher and offer as meat to family members. Shiffer left the farm shortly after he graduated from high school to enlist in the Navy, the relative said.

"He was quiet, maybe a little awkward, but you could tell he was a very smart kid. He had some brainpower," the family member said.

Around 9:15 a.m. Thursday, Shiffer attempted to breach the visitor screening facility at the field office, located on the outskirts of Cincinnati, authorities said. An alarm sounded and armed agents responded, leading Shiffer to flee to his car and onto Interstate 71.

Roughly 20 minutes later, a state trooper located Shiffer's car at a rest area about 20 miles north, but when officers tried to pull him over, he fled and fired a "suspected gun shot," the highway patrol said in its statement Friday morning. He continued north before stopping on a rural road in Chester Township, about 45 miles north of Cincinnati.

He stepped out of the car at about 9:53 a.m. and engaged police in a shootout before taking cover behind the car, launching a standoff that would last until officers shot him around 3:42 p.m., police said.

In a statement Thursday evening, the FBI's Cincinnati field office called the incident an "agent-involved shooting." State police said they are investigating the incident alongside the Ohio Bureau of Criminal Investigation and the FBI.

"The FBI takes all shooting incidents involving our agents or task force members seriously," the statement said. "In accordance with FBI policy, the shooting incident is under investigation by the FBI's Inspection Division."

On Truth Social, a site started by Trump, an account with Shiffer's name published a post after the FBI search at Mar-a-Lago telling others to "get whatever you need to be ready for combat." On Thursday at 9:30 a.m., he wrote another post that seemed to indicate he was writing after attempting to enter the FBI building.

"Well, I thought I had a way through bullet proof glass, and I didn't," he wrote. "If you don't hear from me, it is true I tried attacking the F.B.I., and it'll mean either I was taken off the internet, the F.B.I. got me, or they sent the regular cops."

The Post was unable to confirm that the account belonged to Shiffer.

Experts in extremism and domestic terrorism have warned that violent rhetoric from Republican lawmakers, pro-Trump media figures and anti-government agitators could fuel attacks like the attempted breach of the FBI field office.

"We are likely to see continued acts of violence and attacks," said Ruth Ben-Ghiat, a New York University professor who studies authoritarianism and political violence.

"There is a vast right-wing media and messaging universe, from Fox News to Breitbart to former president Trump to sitting GOP lawmakers like Marjorie Taylor Greene," Ben-Ghiat added, "that traffics in conspiracy theories and seeks to keep people in a state of agitation and fear sufficient to lead some people to make recourse to violence."