The two pilots, an instructor and a student, were from the 138th Fighter Wing in Tulsa, OK, and were in the air for a so-called "tap-the-cap" training mission, Air Force Times reports. The mission simulates a combat air patrol, with the instructor and student flying an oval and waiting for a third F-16 to attack from an unknown direction.
Needless to say, things did not go as planned. According to Air Force Times the USAF report indicates that the instructor mismanaged the situation and the student gave the wrong radio message. This led to two planes just 2,000 feet apart and with 800 knots of closure. For those doing the math at home, that left the pilots less than two seconds to react.
Air Force Times has a comprehensive recap of the Air Force report, including the ultimate findings of the Accident Investigation Board. Head over and have a look.