Monday night'soutside an Ariana Grande concert in Manchester, England isn't the first time terrorists have targeted concert halls or similar stadiums.
The sheer size of these venues creates a challenge for stadium owners and police who are looking to protect potentially tens of thousands of people at once, reports CBS News correspondent Anna Werner.
Panic and confusion spread through the crowd as thousands of young concert-goers reacted to explosions outside the auditorium erupting just minutes after Grande left the stage in Manchester Monday night. Steven Adelman is a venue safety expert.
"It was a target-rich environment for someone with bad intent," Adelman said.
Children were among the. It happened near the ticket area as thousands of patrons were leaving the concert.
"It was simply a lot of people in an area that was very difficult to secure," Adelman said.
The scene in Manchester was reminiscent of other so-called "soft target" attacks includingin November of 2015 inside the Bataclan concert hall where gunmen took the lives of 89 people. That same day security stopped a suicide bomber from entering a Paris soccer stadium.
He then detonated his explosives outside the venue--much like the bomber in Manchester did.
"This is a tragedy, but it's a tragedy about the difficulty that we have securing open space," Adelman said.
Recent terror incidents globally have led to increased security at U.S. concert halls and sports stadiums alike. Some of these measures have been used for years, like undercover guards, closed circuit TV's, magnetometers and hand-wands. Since the Paris attacks, their use is more widespread.
"Safety and security measures that used to only be for the biggest shows are now proliferating across the entire marketplace," Adelman said.
Experts say venue operators could step up security outside their auditoriums to airport-screening levels, but operators may be concerned it would drive customers away.
"What I would say to parents is, don't worry about your child being safe at a concert but the context is, we live in a more dangerous society than we have before," Adelman said.
The U.S. Department of Homeland Security says it has no information to indicate a specific credible threat involving music venues here in the U.S. though it says the public may notice increased security as officials take additional precautions.