No witness recalled seeing the duffel bags being added to the 400 or so backpacks that were already in the cafeteria. The security staff at CHS did not observe the bags being placed in the cafeteria; a custodian was replacing the school security videotape at around 11:14 a.m., which might have been the time that the duffel bags were dropped off. Some internet sleuths claimed that the bomb placement can be seen on the surveillance video at around 10:58 am. Shortly after the massacre, police also investigated whether the bombs were placed during the "after-prom" party held the prior weekend.