On Monday, the FBI released full transcripts of the 911 phone calls between Orlando police and mass shooter Omar Mateen.

Juliette Kayyem, homeland security expert and host of the "Security Mom" podcast, said the transcripts shed light on the pivotal gap in the current timeline of events—the three-hour period that elapsed between when the first shots were fired at 2 a.m. and when the shooter was killed by police at 5 a.m.

"What becomes clear in those transcripts are two things," Kayyem explained. "One, [police] felt from a hostage active shooter situation that so long as he was talking, he wasn't killing—and that appears to be true. They felt like they had some control over the situation."

The second, she said, is that police likely had a difficult time ascertaining the nature of the threat inside the club—and, as a result, were not sure how to respond most effectively.

"[Mateen] was talking about multiple bombs, booby traps—and remember, [police] are getting phone calls from victims are in the bar, leading them in multiple directions, including the belief there was probably more than one shooter," Kayyem said.

A misunderstanding of the nature of the threat inside could explain part of the elapsed time between 2 a.m. and 5 a.m., and—tragically—could have also led to the death of some victims by police fire.

"I think it's likely that we will learn that some of the people killed were killed by friendly fire. That would explain why [police] retracted. They may have gone in, realized they didn't have control over the situation, and retracted," Kayyem said.

That's why it's so important to get a full picture of what went on inside the Pulse Nightclub that night—to make sure police are better equipped to deal with these situations in the future.

"That's why we need to do after-actions, why we need to release the transcripts, why the Orlando police should not be defensive. This was a unique and horrible situation, but we need to learn because obviously these situations will happen again," Kayyem said.

To hear more from Juliette Kayyem, tune in to Boston Public Radio above.