The mass shooting at the Route 91 Harvest Festival in Las Vegas this weekend is, sadly, not the first time a large public event has been under attack in recent memory.
In this case, however, the concert was outdoors and totally open. It was designed for maximum capacity and enjoyment, but exposed vulnerabilities that security officials may not have considered.
So the question we must ask ourselves is: how we can secure these spaces better? Is it even possible?
"The... concern is the unique aspect of this attack," said Errol Southers, a counter-terrorism expert at USC. "We've been focused for the last several years on venues specifically that host or can occupy large numbers of people - stadiums, concert venues - but here we have now a shooter...who decides to attack thousands of people from an elevated position almost military style."
It's a situation that presents a whole new set of concerns for security officials. "In an outdoor event you are literally cooped up...and you are limited with regards to a shelter-in-place option, " said Southers, adding that this will be a major factor in conversations among security officials going forward.
"We will certainly be looking at elevated positions from open-air events like this in the future and I think they may decide to increase the number of exits accessible to people," said Southers. "But at the end of the day, as the sheriff said yesterday, an event like this is really difficult, or even impossible, to prevent from happening."
To hear the whole interview with Errol Southers about securing open spaces, click on the blue player above.