Experts are questioning why police held off for several hours before storming the Florida nightclub where a gunman shot more than 100 people.

Law-enforcement leaders say lessons learned from other mass shootings suggest it's vital that police confront an attacker rather than wait to assess the situation.

As the shooting began Sunday, an off-duty police officer working at the Orlando club exchanged gunfire with the suspect. But three hours passed before SWAT team members stormed the building and ended the attack.

Chris Grollnek is an expert on active-shooter tactics and a retired police officer and SWAT team member. He says "action beats inaction 100 percent of the time."

It's not clear yet what information authorities in Orlando had and how the decisions were made.