The question has been asked by many in the days following the deadliest mass shooting in modern U.S. history as to why it took Orlando Police three hours to neutralize terrorist Omar Mateen.

Mateen launched his attack on the gay nightclub in Orlando, Fla., around 2 a.m. Sunday, yet the ordeal didn’t end until three hours later. 

Police say that during those three hours, they were rescuing clubgoers and employees and trying to assess whether the gunman’s boasts — he claimed to have an explosive vest — were real. In an interview with the Los Angeles Times , the commander of the Orlando Police Department SWAT team described the challenges his officers faced and how they made key decisions that morning.

“Officers were running inside and grabbing people and throwing them in pickup trucks” to be taken to hospitals, said Capt. Mark Canty of the SWAT team. “There was never a time we were sitting there twiddling our thumbs. My guys were doing things from the beginning. We weren’t just sitting idly by. We were doing what we needed to do to save lives.”