New document sheds light on role of K9s during Pulse attack

When Omar Mateen claimed to have explosives during the Pulse nightclub shooting rampage in June, two bomb-sniffing dogs got a "positive hit" on his vehicle outside the gay bar.

While authorities investigated, many of the hundreds of first responders on the scene were ordered to back away from a perimeter that had been set up around the gay nightclub. That's according to a timeline of events obtained by The Associated Press through a public records request.

Command centers were also relocated as a precaution. As it turns out, there were no explosives in the car. Instead, it was ammunition and weapons.

The timeline offers new insight into the police and firefighter response to the worst mass shooting in modern U.S. history.