Surveillance footage released on July 12 showed an unidentified man inside the school using hand sanitizer about an hour after the gunman entered the building.
The moment in question took place at 12:30 p.m. local time. The footage also showed the same man looking down at his phone several times.
Near the beginning of the surveillance video, at around the five-minute mark in the above-linked YouTube clip, the gunman could be seen at a classroom door. Uniformed law-enforcement officers were shown arriving at the same classroom door just two minutes and 40 seconds later. However, officers did not enter the classroom until more than an hour later, the footage showed.
In total, the surveillance footage showed that around 77 minutes passed between the moment the shooter entered the classroom and when officers engaged with him.