A retired La Crosse police officer says the public needs to do more to prevent mass shootings from happening in the future.
"The time for denial has passed. You can not say it's not going to happen here. It's not going to happen to me," said Dan Marcou, a retired lieutenant with 33 years of law enforcement experience.
"You have to pay attention but there are some things you can do. We're not helpless in this," said Marcou, who now trains law enforcement officers how to best engage and take down an active shooter.
"You wish we didn't have to think like this but it's a different world that we live in," he said.
While Marcou says it's important to train officers on how to deal with people looking to inflict mass casualties, he says the public needs to be trained as well.
Click here to read Marcou's research on the 5 phases of an active shooter.
Marcou's research has found that most of the perpetrators go through the same phases leading up to the shooting. Most will draw or write about their plans and some even tell others. He says almost all show some warning signs.
"There's a certain amount of denial that 'this can't happen here' or 'I can't be seeing what I'm seeing'. We need to stop that," he said.
Marcou says it's those early phases of plotting a mass shooting where lives can be saved. Once the shooter is on their way to their chosen location, it's almost always too late.
"All I know is that the people that pick up a gun seem to have no empathy and they seem to be looking for a top score," said Marcou.
It's like a twisted video game, but real.
"The days of this guy isn't serious need to be over."