At a press conference a few hours after the Pulse Nightclub shootings ended, Orlando Police Chief John Mina sketched out the broad strokes of a massacre that began just after 2 a.m. when an off-duty cop working security responded to shots fired.

“Our officer engaged in a gun battle with that suspect. At some point the suspect went back inside the club where more shots were fired,” Mina said. Five more police officers broke a window and climbed in a few minutes after the attack began:

At 2:08, according to a timeline released by the FBI, “Officers from various law enforcement agencies made entrance to Pulse and engaged the shooter.”

But as new bits of information about the shootings continue to trickle out, so do apparent inconsistencies in the law enforcement account of their response.

“When those officers entered the building, the shooting stopped,” Chief Mina wrote in an email. It is unclear, then, what it means that officers from various agencies “engaged the shooter.”

“This did turn into a hostage situation,” Chief Mina told reporters the day of the attack. A month later, the remaining question is how. Police said the hostage scenario began when officers cornered the gunman in the bathroom area and took control of the rest of the club, roughly 10 minutes after the attack began. That prompted a shift in tactics from active-shooter to a hostage situation and is the main reason police have given for waiting nearly three hours to storm the building and kill the gunman.

There are two moments when a hostage is at greatest risk of serious injury or death -- one, when they're being taken hostage, and two, when a rescue takes place. -Thor Eells

“There are two moments when a hostage is at greatest risk of serious injury or death,” explains Thor Eells, chairman of the NTOA, or National Tactical Officers Assocation, a membership group for SWAT officers. “One, when they’re being taken hostage, and two, when a rescue takes place.”

Eells was briefed by SWAT officers who were on the scene in Orlando. “The last thing law enforcement wants to do is be the proximate cause of additional casualties,” he says.

But that logic doesn’t mesh with the police’s own timeline, which has an Orlando Police Department officer firing shots at the gunman a full six minutes after the hostage situation began.

After that, police said the shooting stopped, for reasons that are still unclear.

“Whenever there’s still people dying, and he has the potential to shoot somebody, it can never stop,” says Grant Whitus, an active-shooter response trainer who was one of the first SWAT officers on the scene at Columbine, Colorado in 1999. “You go in that room and you finish it, because if you don’t finish it, innocent people are going to die.”

When you show the objective is to kill people, and you've already demonstrated your willingness to do so, there's nothing to talk about. -Chris Grollnek

Whitus says that thinking is at the core of active-shooter training today precisely because of Columbine, where law enforcement came to believe a delayed response cost additional lives. “You’ve got to get in and end it as quick as possible and then get aid to all those people that need it.”

The Orlando police have maintained all along that no shots were fired between 2:18 a.m. and the moment, nearly three hours later, when the SWAT team stormed the building. Dozens of people were pulled from the club and transported to the hospital during that interval.

Even so, Chris Grollnek says those rescues don’t explain the decision to stop shooting at the gunman when there were still dozens more people trapped in club bathrooms. “Somebody made the decision to turn it into a barricaded person and send negotiatiors.”

Grollnek is a Texas-based active-shooter prevention expert. “When you show the objective is to kill people, and you’ve already demonstrated your willingness to do so, there’s nothing to talk about,” he said.

Miami Beach Police Chief Dan Oates, who was police chief in Aurora, Colorado during the movie theater shooting there in 2012, cautions against drawing conclusions from the fragmented accounts that have come out so far. “No one knows what happened there other than the officers that responded and the people that were there.”

Oates stresses how confusing these events can be for eyewitnesses. For instance, “Everybody always sees more shooters than there are. In Columbine there were two actual shooters and cops were told there were six. In Aurora, we were being told there were multiple shooters when there was only one.”

Whatever lessons eventually emerge from Orlando, Oates says, one more tragedy of America’s mass shootings is that police have so many opportunities to learn from past mistakes.