Days after this car bombing, military commanders briefed soldiers and airmen at Khobar that the U.S. had received anonymous communications from an organization claiming to have carried out the Riyadh attack.

Al-Mughassil, Al-Houri, Al-Sayegh, Al-Qassab, and the unidentified Lebanese man bought a large latrine service tanker truck in early June 1996 in Saudi Arabia.

When they were denied access by U.S. military personnel, at around 9:43 p.m. local time, they drove a Datsun scout vehicle,[9] another car and the bomb truck, to a parking lot adjacent to building #131.

Several military vehicles parked to the left side of building #131 suffered no direct impact from debris, but were heavily damaged by the sheer intensity of the shock wave.

In all, 19 U.S. Air Force personnel were killed: After the blast, an assessment crew consisting of the Central Intelligence Agency (CIA), Federal Bureau of Investigation (FBI), Diplomatic Security Service (DSS), and United States Air Force Office of Special Investigations (AFOSI) was sent to assess the risk to other security compounds in Saudi Arabia, and to offer suggestions for the Khobar Towers complex.

According to the New York Times, "significant shortcomings in planning, intelligence, and basic security left American forces in Saudi Arabia vulnerable.

"[12] Numerous warnings had been made available to the intelligence community and military command, and up to "ten incidents [were] reported suggesting that the Khobar Towers are under surveillance" from April to June 1996.

[12] American commanders were also blamed, as they had not taken every precaution advised by the Pentagon; specifically, because "the project was deemed too costly",[12] they had failed to implement a recommendation to coat Khobar's windows with plastic to prevent flying glass.

"[17] In April 1997, the Chairman of the Joint Chiefs of Staff, Gen. John Shalikashvili, said that the Pentagon did not have sufficient evidence about the bombers to consider retaliation against foreign countries that may have played a role.

[21] In August 2015, Arab newspaper Asharq Al-Awsat reported that Ahmed Ibrahim Al-Mughassil, a leader of the gulf shia group Hezbollah Al-Hejaz found to be responsible for the bombing, had been arrested in Beirut and transferred to Saudi Arabian custody; an anonymous American intelligence officer told The New York Times that the Saudi government had not confirmed the arrest, but U.S. intelligence believed the report was accurate.

As if to make the point that they might have been chased out of Sudan by Saudi Arabia and the US they were not leaving with their tails between their legs, al Qaeda struck again: The June bombing of Khobar Towers.

According to the United States, classified evidence suggests that the government of Iran was the key sponsor of the incident, and several high-ranking members of their military may have been involved.

Within days of the blast, counterterrorism officials on Clinton’s National Security Council staff concluded that elements inside Iran, specifically the Islamic Revolutionary Guard Corps (IRGC), were the perpetrators.

[31] Clinton, who had initially taken a stand toward the Islamic Republic, including imposing major economic sanctions on the country, reversed his thinking in the hope that Khatami potentially represented a game-changing shift in Iran's conduct.

The prospect of an opening with Tehran, which intrigued many U.S. allies and even domestic critics of administration policy, drove Clinton's response to the Khobar attack.

The White House and State Department sent various signals to the Iranians, some of which they reciprocated, but ultimately hopes for a significant improvement in relations remained unfulfilled.

Delivered by Omani Foreign Minister Yousef bin Alawi in July, the letter attempted to achieve multiple purposes: to signal Tehran that Washington was open to a rapprochement but also to make clear that the United States held the IRGC responsible for the bombing.

Although Khatami was reportedly happy with the American initiative, especially because it was accompanied by an oral message of strong personal support from Clinton delivered by the Omani envoy, the Iranian president's colleagues in the leadership, including Supreme Leader Ali Khamenei, reacted vehemently to the text of the letter.

[35] Beyond the Clinton administration's miscalculation of Iranian politics, the episode showed that the bombing would continue to cast a long shadow over U.S.–Iran relations in years to come.