Even if an after-action investigation is released, a lack of national standards leads to wide variability in the detail of information in reports, ProPublica, The Texas Tribune and FRONTLINE found.

During an October conference to prepare law enforcement for dealing with an active shooter, Nevada State Police department Lt. Jacob Fisher played body camera footage that showed what he believed was a key misstep during the country’s deadliest mass shooting.

The footage from the 2017 massacre at the Mandalay Bay Resort and Casino showed a veteran Las Vegas Metropolitan Police officer and his trainee waiting on the floor below the shooter instead of confronting him as he spewed gunfire into the crowd of concertgoers outside. Six years later, Fisher told the room full of law enforcement officers and firefighters at the conference in Grapevine, Texas, that he had trained the veteran officer and felt like he had failed.