Department of Homeland Security investigators are probing whether a staff member was trying to attack their DC headquarters after he was allegedly caught smuggling a cache of weapons inside.

Jonathan Wienke, an analyst for DHS and a former Army medic, was caught carrying a revolver, a knife, handcuffs, pepper spray and an infrared camera into his workplace on June 9, agents say.

Investigators say Wienke 'was conspiring with another to commit workplace violence, and... may have been conspiring or planning to commit violence against senior DHS officials in the building.'

Jonathan Wienke, an analyst for DHS and a former Army medic, is accused of plotting to attack senior federal officials after being caught bringing a revolver, knife, handcuffs and pepper spray into work

Wienke, who has top-secret security clearance, was arriving at work around 7.30am when he was randomly selected for security screening as he made his way inside, federal investigators say.

After his backpack was placed into a scanner officials say they discovered a folding knife with three-inch blade, two hand-held radios, handcuffs and pepper spray, along with various other items.

Officers seized the knife and spray, but remarkably Wienke was allowed to enter the building without any further checks taking place.

Wienke was selected for a random security screening on the morning of June 9 when officials discovered the knife and spray in his backpack

It was only at 9am, an hour and a half after the initial search, that Special Agent Eric Mann and another officer went to Wienke's desk to carry out a follow-up pat down.

Despite insisting that he was not carrying any other weapons, Mann discovered a five-shot revolver loaded with .22-caliber hollow-point rounds in the front pocket of Wienke's pants.

After the weapon was discovered, Wienke uttered an 'audible expletive', according to Mann.

Wienke was arrested and the following day was charged with carrying a pistol without a license and released on June 13, documents show.

In an application for a search warrant on Wienke's house, Mann listed the charges against him as attempt and conspiracy to assassinate, kidnap or assault a member of the executive branch of the government, false impersonation of a federal officer and possession of a firearm in a federal facility.

It is unclear what officers found while searching the property, located in Martinsburg, West Virginia, 75 miles from the office, or whether additional charges are being filed against the employee.

Wienke has been placed on administrative leave while the investigation is carried out, Scott McConnell, a spokesman for the Department of Homeland Security, said.

Social media accounts linked to Wienke reveal he studied at the University of Central Michigan, graduating with a degree in computer science.

He then went on to serve as a technician in the Air Force, followed by work as a programmer and photographer before going into the Army as a medic.

Wienke later worked as a photographer at the Capitol building and for the National Reconnaissance Office before going back into the Army, then taking his current role at DHS.

Despite discovering the knife, Wienke was allowed inside the building without further searches, and officials only discovered the revolver after carrying out a follow-up search at his desk

Back in 2012, Wienke launched a bizarre and since-deleted Facebook rant about the Sesame Street's Big Bird, accusing the fictional children's character of being 'part of the 1%'.

Wienke apparently objected to federal funding being given to Sesame Workshop, the production house behind the TV show, because the company has 'an income stream whose size and diversity is the envy of most 1-percenters.'

He concludes: 'I have no quibble with the educational value of Sesame Street, and it's producers deserve the success they've obviously achieved.