Osama bin Laden was planning to attack the U.S. this September, on the 10th anniversary of 9/11, The Wall Street Journal reports. That information comes from a "treasure trove" of materials that was seized from the compound in Abbottabad, Pakistan, where bin Laden was killed this spring. Here, a brief guide to bin Laden's array of rough plans:

What kinds of attack were being plotted?
Bin Laden was enthusiastic about carrying out an attack on "dates of symbolic significance," like July 4 or Sept. 11, says Siobhan Gorman at The Wall Street Journal. Bin Laden and operations chief Attiyah al-Rahman had reportedly begun recruiting and building an attack team for a mission to take place on Sept. 11, 2011, which may have targeted a train. According to ABC News, bin Laden was also "obsessed" with planes as a terrorist weapon, and wanted to fly a small airplane into a major sporting event, causing mass casualties.

Did any of bin Laden's plans have specific human targets?
President Obama was a "primary target on bin Laden's hit list," says Martha Raddatz at ABC News. Officials say that one plan hatched by bin Laden involved shooting down Air Force One or the presidential helicopter, Marine One. Gen. David Petraeus, who was commander of forces in Afghanistan and now heads up the CIA, was also a target. Bin Laden hoped to kill him in the same way, by attacking him in the air.

How far along were these plots?
The plans hadn't gone further than the "discussion phase," according to the Journal. There were no signs from bin Laden's correspondence with al-Rahman that the schemes "ever went beyond early planning." The terrorist ringleader's attack team was far from assembled, as he "repeatedly rejected" names suggested to him by al-Rahman.

Where exactly do these details come from?
The communication between bin Laden and al-Rahman were stored on documents saved to flash drives, which were obtained in the raid on bin Laden's compound. The raid yielded several computers, almost a dozen hard drives, and approximately 100 other data storage devices. Counterterrorism officials from a half dozen U.S. agencies reviewed the materials and submitted detailed reports from their findings.

Could attacks like these actually happen?
An attack at a sporting event is feasible, says former FBI special agent Brad Garrett, as quoted by ABC News. "We have so many small airports, you could fly below radar." But it's very unlikely that any aircraft carrying President Obama or Gen. Petraeus could be shot down. "It's difficult, but not impossible," Garrett says. "The reality is because of the countermeasures and other planes and helicopters in the air, it's not a likely scenario."

Sources: ABC News, Boston GlobeWall Street Journal