WASHINGTON -- Federal prosecutors are investigating whether a Department of Homeland Security employee with top-secret clearance was planning an attack at the agency's Washington headquarters when he entered the building with a gun, a knife, an infrared camera, pepper spray and handcuffs.

Jonathan Wienke, and analyst in the Office of Intelligence and Analysis, allegedly carried the weapons into the building on the morning of June 9. Court documents filed by the federal government state that investigators have probable cause to believe Wienke "was conspiring with another to commit workplace violence, and more particularly may have been conspiring or planning to commit violence against senior DHS officials in the building."

Bill Miller, a spokesman for the U.S. Attorney's Office for the District of Columbia, declined to comment on the documents. He said Wienke was charged on June 10 with carrying a pistol without a license and was released on June 13 pending further court proceedings. The case remains under investigation, Miller said in an email.

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

The federal government searched his home in Martinsburg, West Virginia, a 75-mile commute from the office. In the affidavit for the search warrant, Department of Homeland Security Special Agent Eric Mann described the series of events that led the government to suspect Wienke was potentially plotting an attack.

At 7:30 a.m. on June 9, Wienke entered the building, which has a security level on par with the White House and the Pentagon, according to Mann's affidavit. Security measures include random screening at the door; Wienke was selected and his backpack was placed in a screening machine.

Security officers found a folding knife with a 3-inch blade, two hand-held radios, pepper spray, an infrared camera and a set of handcuffs, among other items, the affidavit states. The officers seized the knife and spray.

At 9 a.m. Mann and another officer followed up with Wienke at his cubicle, directly across from where senior officials were meeting, the documents say.

He gave them permission to search him and denied he was carrying any additional weapons, the affidavit alleges. Mann wrote that he patted Wienke down and discovered a five-shot revolver loaded with .22-caliber hollow-point rounds in the front pocket of his pants. He wrote that he heard Wienke "utter an audible expletive."

A man who answered the phone at a number listed for Wienke hung up when asked for a comment Tuesday evening. An email sent to Wienke was not immediately returned.

In his affidavit for a search warrant, Mann listed the potential crimes 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 in the documents what officers found in his home, or whether prosecutors intend to pursue additional charges.