Social media accounts thought to belong to FBI shooting suspect Ricky Shiffer have come under scrutiny since his death on Thursday following a shoot-out with officers and an attempted attack on the bureau’s office in Cincinnati.

One tweet seen by NBC News suggested that in May, Shiffer responded to a tweet by pro-Trump congresswoman Marjorie Taylor Greene by referencing the need for a repeat of “1775” – in apparent reference to the beginning of the American Revolutionary War.

Shiffer reportedly wrote: “Congresswoman Greene, they got away with fixing elections in plain sight. It’s over. The next step is the one we used in 1775.”

Ms Greene had tweeted: “I know they are trying 1984, but I’m feeling 2016 vibes”. Those comments were in apparent reference to false claims made by Donald Trump that Democrats stole the 2020 US election.

Analysis of the FBI attack suspect’s social media history by Huffington Post suggests he also tweeted about support for the Proud Boys, the far right militia group connected to January 6.

Social media posts under the name Ricky Shiffer suggest the suspect in Thursday’s attack in Cincinnati called on others to “Save ammunition” and “Get in touch with the Proud Boys”, analysis from a think tank shows.

The Institute for Strategic Dialogue, a think tank that monitors extremism and online hate speech, shared with ABC News on Friday its analysis of posts believed to be made by Shiffer.

As well as content on Twitter and Donald Trump’s own platform Truth Social, Shiffer is believed to have posted on the video streaming website Rumble, the report said.

Officials have been reported as saying that Shiffer’s connections to far right groups are under investigation and that he has been classified a “suspected domestic violent extremist”. That remains to be confirmed.

FBI officials have warned of a rise in threats against federal agents since the execution of a search warrant on Donald Trump’s Mar-a-Lago property on Tuesday.

The search, which a law enforcement official suggested to The Washington Post was in connection with an investigation into classified nuclear documents allegedly kept at Mar-a-Lago by Mr Trump, came days before the FBI’s office was attacked in Cincinnati.

Mr Trump’s supporters have heavily criticised the FBI’s search, accusing the bureau and the Justice Department of using the legal system as a political weapon. That is despite the reports of declassified nuclear documents being seized at Mar-a-Lago however.

On Wednesday, FBI personnel were warned to avoid protesters and to avoid showing their security keys in public as a result of an increase in threats made against the bureau by far right social media accounts. The follwowing day, suspect Ricky Shiffer attempted to breach a FBI building.

Ricky Shiffer, the Ohio man who died in an armed standoff with police on Thursday after attacking an FBI field office in Cincinnati, was a military veteran.

The 42-year-old served in the Navy on a nuclear submarine and later in the National Guard, Military.com reports.

Shiffer was in the Navy between 1998 and 2003, serving as a fire control technician and operating onboard the nuclear-powered USS Columbia in Pearl Harbor, Hawaii, earning no awards or decorations. The position meant he was responsible for the systems used to maintain and fire the craft’s advanced weapons.

More details on the breaking news story here.

Ricky Shiffer, the Ohio man who died in an armed standoff with police on Thursday after attacking an FBI field office, was a military veteran.

The 42-year-old served in the Navy on a nuclear submarine and later in the National Guard, Military.com reports.

Shiffer was in the Navy between 1998 and 2003, serving as a fire control technician and operating onboard the USS Columbia in Pearl Harbor, Hawaii, earning no awards or decorations.

He followed his time on the sub with three years in the Florida National Guard as an infantryman, deploying to Iraq then being honourably discharged in 2011, according to records from the military branch.

On Friday, Republican congressman Mike Turner reportedly became the first Republican lawmaker from Ohio to address the attack on the FBI office in Cincinnati.

Speaking during a press briefing on Friday, the Ohio Republican said all members of the House Intelligence Committee “are in full support of the men and women who everyday work to keep our nation safe and we condemn any action of violence”.

He went on to question the FBI’s search of Mar-a-Lago however and said his committee has “serious questions” about the Justice Department’s authorisation of the FBI search on former Republican president Donald Trump’s Florida property.

The GOP has been condemned by Democrats for criticism of the FBI and Attorney General Merrick Garland, who said on Thursday that his department did not take authorisation of a search warrant against Mr Trump “lightly”.

Federal officials were looking into Ricky Shiffer for months, long before the Ohio gunman attacked an FBI office in Cincinnati on Thursday and was killed in a firefight with police.

Officials were looking into whether Shiffer was involved in the January 6 attack on the US Capitol or tied to extremist groups there, the New York Times reports.

A neighbour told the Times that federal agents had showed up at their apartment complex and asked questions.

Social media accounts appearing to belong to Shiffer posted about being at the January 6 riot.

Sherrod Brown, a Democrat senator for Ohio, tweeted on Thursday that the attempted assault on the FBI’s field office in Cincinnati was “an appalling attack on law enforcement”.

Social media messages seen by news outlets before they became unavailable suggest Ricky Shiffer, the suspect in the attack on the FBI office in Ohio, had called for the deaths of FBI personnel.

On Donald Trump’s Truth Social media platform, an account belonging to a Ricky Shiffer had posted a “call to arms” and urged people to arm themselves and “be ready for combat” after the search, the Associated Press reported.

At least one of the messages on Truth Social appeared to have been posted after Shiffer failed to break into the FBI building in Cincinnati. It read: “If you don’t hear from me, it is true I tried attacking the FBI”.

Law enforcement officials are analysing the social media posts and told ABC News on Friday that the suspect is a “suspected domestic violent extremist”.

It was also thought that Shiffer had attended the January 6 Capitol riot with other Trump supporters.