PORTLAND, Ore. -- Even before the chaos began to clear in Las Vegas, Portland criminologist Randy Blazak had a pretty good hunch about the motivation behind the shooter.

“They start as a desire for suicide. But a suicide that's spectacular,” he said.

Blazak wrote a book about mass shootings in 2001 and said most start with the gunman losing something --money, a marriage, their job. They typically have no social network where they can talk it out and they snap, he said.

“We've seen this in other examples where people shoot up their work place or people shoot up sort of public spaces because they feel like they've lost everything and they want everyone to share their pain and screw the world I'm gonna go out in a hail of bullets,” Blazak said.

So how can we protect ourselves?

There are after all tall buildings in Portland around Providences Park, where thousands gather for football and soccer games.

And Pioneer Court House Square which hosts concerts and protests and rallies.

“It’s going into an event and playing that ’what if’ game over and over and over again,” said Scott Castleman.

He owns a security company called Corporate Crime Control Association, and has studied the industry for 25 years.

He said places can only do so much for security — we, the public, have to do the rest. And that includes looking for exits when you enter a public place and thinking about what you would do if something happened to your left or right, for example.

He said it’s important to plan an escape route every time you go to a public gathering.

“It’s learning to make that decision when something happens -- if there's gunfire that’s erupting and it’s near you, making that decision to actually do something about it. And not freeze. Most people who become victims? It’s because they froze,” Castleman said.

Finally, he said we need to speak up if we see something odd.

“I think a lot of these things can be prevented if they see something suspicious that they alert somebody to it but there are too many people that are like, 'well I should say something but I don’t want to raise suspicion or I don’t wanna, I don’t wanna scare people',” he said.