Follow up investigations centered on Chris Kriegman and Andre Kriegman's parents.
The most striking and unusual feature of this incident was the documentary footage that the perpetrators furnished. At the outset, detectives and officers watched all the footage in its entirety. When officers retrieved the video camera in Kriegman's vehicle, they found a video suicide letter on the tape inside. Also on the tape was footage of Kriegman and Gabriel breaking into Chris Kriegman's apartment and stealing firearms owned by him. The tape ended with footage of Kriegman and Gabriel in the car immediately before the assault.
Before they left the car, they turned the camera on and left it running (using this footage, and comparing the intervals between gunshots on the soundtrack, investigators were able to construct a fairly precise timeline of events).
In the suicide statement, there was a reference to more video footage in a safety deposit box. Detectives who went to the bank found approximately 34 hours of video footage.
Detectives examined the footage to determine whether or not anyone else was involved in the planning or execution of the attack. Investigators assumed that Kriegman and Gabriel were obfuscating pertinent facts in the tapes.