ORLANDO, Fla. (AP) - 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 nightclub, 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, it was ammunition and weapons, not explosives in the car, according to dispatcher logs and the timeline.
The timeline offers new insight into the police and firefighter response to the worst mass shooting in modern U.S. history, particularly the role that the bomb dogs played and how first-responders reacted to the dogs' hit. The FBI is still investigating the massacre. A spokeswoman said she couldn't comment on when the investigation would be finished.
Clearly, the devastation could have been much worse if the car had explosives and precautions weren't taken. In all, 49 patrons were killed and dozens others were injured. During calls with police negotiators and a 911 operator, Mateen pledged allegiance to the Islamic State.
After the dogs had the positive hit, "all groups are systematically relocated to put 2 city blocks between themselves and the scene," according to the timeline that is part of a power point presentation given by the chiefs of the Orlando Fire Department and Orange County Fire Rescue.
Adding to the confusion, some hostages texted that Mateen had bomb vests that he intended to place on patrons, a claim that also ended up being false.
It's hard to say how much time, if any, was lost moving around first responders during the standoff, which lasted from a about 2-5 a.m. on June 12. The fire departments' presentation indicates that the dogs started their search shortly after 3:40 a.m., and a police log shows that one of the dogs detected the ammunition in the car by 4:06 a.m.
A dispatcher log entry from the Orange County Sheriff's Office, which assisted the Orlando Police, says, at 4:08 a.m.: "Need to move out perimeter."
Orlando Fire Department spokeswoman Ashley Papagni said Mateen's vehicle was officially cleared at 11:02 a.m. But authorities determined there weren't explosives much earlier. SWAT team members began to breach a wall to get out hostages trapped in bathrooms a little after 5 a.m., according to the timeline. Mateen was killed in a shootout with SWAT team members shortly before 5:20 a.m.
The timeline also offers some "lessons learned." They include sticking to official radio channels when communicating between fire and police command centers, instead of using informal conversations, and creating a system to better count the number of patients going to hospitals. The timeline said the informal communication hampered firefighters' learning about the wall breach and anticipating the next wave of patrons needing medical attention.
In an interview, Orlando Police Chief John Mina took issue with calling the bomb dogs' hit "a false-positive" since the dogs did detect one of the 22 items they are trained to pick up.
Even though some first responders relocated, SWAT team members didn't change their position and officers continued to remove people from the club, Mina said.
"They continued their response. They didn't back off," Mina said.
Paramedics also never stopped treating patrons, Papagni said.
Dogs typically are trained to detect odors like nitrates, and they don't differentiate whether they've encountered a bomb or ammunition, which both can have nitrates, said David Latimer, a master K9 trainer based in the Dothan, Alabama, area.
"What he's saying when he makes a hit is 'I smell an odor which is consistent with what will get me my toy,'" Latimer said.