In the five months leading up to this year’s 9/11 anniversary, there were two bombings on the U.S. consulate in Benghazi and increasing threats to and attacks on the Libyan nationals hired to provide security at the U.S. missions in Tripoli and Benghazi.

Details on these alleged incidents stem in part from the testimony of a handful of whistleblowers who approached the House Committee on Oversight and Government Reform in the days and weeks following the attack on the Benghazi consulate. The incidents are disclosed in a letter to be sent Tuesday to Hillary Clinton from Rep. Darrell Issa, the chairman of the House Committee on Oversight and Government Reform, and Rep. Jason Chaffetz, the chairman of the oversight committee’s subcommittee that deals with national security.

The State Department did not offer comment on the record last night.

The new information disclosed in the letter obtained by The Daily Beast strongly suggests the U.S. consulate in Benghazi and the late Ambassador Chris Stevens were known by U.S. security personnel to be targets for terrorists. Indeed, the terrorists made their threats openly on Facebook.

For example, following a May 22 early-morning attack on a facility that housed the International Committee on the Red Cross, a Facebook page claimed responsibility, and said the attack was a warning and a “message for the Americans disturbing the skies over Derna.” That reference was likely to American surveillance drones over a city that provided fighters to al Qaeda in Iraq in the last decade.

In June a Facebook page associated with militants linked to the late Libyan dictator Muammar Gaddafi posted a threat to Stevens based on the route he took for his morning jog. The Facebook page also posted a picture of Stevens. The letter to Clinton notes that “after stopping these morning runs for about a week, the Ambassador resumed them.”

A senior State Department official contacted for this story said the ambassador was “not reckless” with his own security or that of his staff. But this official also acknowledged that the ambassador was “an old-school diplomat” and strongly desired to have as few barriers between himself and the Libyan people.

The letter also discloses for the first time a bombing at the U.S. consulate that occurred on April 6, 2012. It says that on that day, two former security guards for the consulate in Benghazi threw homemade improvised explosives over the consulate fence. That incident resulted in no casualties. The Wall Street Journal first reported last month that on June 6 militants detonated an explosive at the perimeter gate of the consulate, blowing a hole through the barrier. The letter to Clinton quotes one source who described the crater as “big enough for forty men to go through.”

Obama administration officials have said there was no specific intelligence predicting the 9/11 anniversary assault on the U.S. consulate in Benghazi. A senior State Department official acknowledged that there were five serious attacks on Western targets since the spring in the lead-up to the attack on the 9/11 anniversary. Speaking of the June 6 attack at the consulate’s perimeter gate, this official said, “The IED attack caused no loss of life and no injury. The wall acted as designed. It absorbed it.” This official said that compared with the 9/11 anniversary assault, the earlier attacks in Benghazi were mild. “We faced a coordinated, military-style assault. We’ve never seen that kind of attack before,” this official added.

Until Sept. 19, eight days after the consulate attack, senior administration officials had said it resulted spontaneously from riots at the U.S. embassy in Cairo against an Internet video denigrating the Muslim prophet. Spokesmen for the State Department and the National Security Council did not return emails late Monday evening.

Rep. Chaffetz told The Daily Beast Monday that the allegations detailed in the letter were based on whistleblowers he described as “people who have firsthand knowledge of the incidents themselves.” Chaffetz declined to provide more details about the whistleblowers other than to say they were U.S. government employees and there were fewer than 10 of them.

In some cases the incidents against U.S. personnel or Libyans working to protect U.S. personnel were mild. In April a U.S. foreign-service officer stationed in Benghazi was attending a “trade-related event” at the International Medical University when the security forces of the university got into a fistfight and then a gunfight with the security detail for the trade delegation. Eventually the American officer had to be evacuated by the local Libyan militia that provided security for the consulate, known as the February 17 Brigade.

On May 1 at the U.S. Embassy in Tripoli, the deputy commander of the embassy’s local security force was “carjacked, beaten, and detained by a group of armed youth.” Eventually the man escaped his captors and phoned the embassy. “Libyan security forces fought a gun battle with the assailants in order to recover a number of stolen vehicles and release other detainees,” the letter says.

Security deteriorated significantly in June. On June 10, a man fired a rocket-propelled grenade in broad daylight into a convoy carrying the British ambassador to Libya. Later that month, the Red Cross was attacked again. By the end of June, the British Consulate and the Red Cross closed their facilities in Benghazi. By the start of July, the U.S. Consulate was one of the only Western targets left in the city.

“This was not a safe country on its way to a normalized situation. It was a very volatile situation,” Chaffetz told The Daily Beast.

The House Oversight Committee is expected to hold a hearing on Oct. 10 on the threats leading up to the attack.