The explosion at an Ariana Grande concert in the British city of Manchester killed at least 19 people and injured dozens. It is raising new questions about how authorities can better protect large venues.
What we know
The explosion happened near an entrance to the 21,000-seat Manchester Arena just minutes after Grande's concert ended with the song "Dangerous Woman" and the singer left the stage, witnesses said.
British counter-terrorism investigators think the attack may have been the work of a suicide bomber who entered a crowded area outside the performance space where attendees were streaming out of the concert, according to U.S. law enforcement sources briefed on the investigation.
They cautioned that all information is preliminary and video from security cameras will allow investigators to reconstruct the deadly events. A law enforcement official and a witness said the explosion happened near an entrance where fans typically pick up tickets.
Protecting vulnerable points in the crowd
Michael Downing, executive vice president of security for Prevent Advisors, which specializes in arena and stadium security, said many American and European venues already use metal detectors, bomb detection technology and armies of security guards and cameras inside the facilities.
But the Manchester incident shows the need for more vigilance in areas outside those security zones, such as transportation centers, walkways and parking lots, said Downing, the former head of counter-terrorism for the Los Angeles Police Department.
"Obviously, we are going to have look at ingress and egress," he said.
He said Los Angeles law enforcement already monitors ingress and egress points at major events such as award shows and special sporting events such as world championships. But Manchester and recent acts of terrorism in Europe suggest more needs to be done, he said.
Terrorists tend to target areas where large crowds gather. Attacks in recent years in Berlin, Paris and Nice, France, have prompted Southern California law enforcement officials to review security measure at train stations and venues such as Staples Center and Dodger Stadium.
But this is a long-running issue that dates back to at least the 9/11 attacks. Security experts have long expressed concerns about a possible terrorism incident at Los Angeles International Airport not inside the terminals but outside where passengers sometimes are forced to line up. LAX has been working to reduce lines forming outside.
Are ‘vapor wake’ dogs the answer?
Downing said "vapor wake" dogs with more sensitive noses and different training from traditional bomb-sniffing canines can detect suicide bombers.
Traditional bomb-sniffing dogs are trained to smell specific objects. Vapor wake dogs are trained to smell particles in the air and can detect explosives worn on a person even in crowded areas and venues. Such dogs are already employed by the New York Police Department's counter-terrorism operations, he said. The Los Angeles Police Department also has two of the dogs.
Brian Levin, a terrorism expert and professor at Cal State San Bernardino, said the British have some of the most sophisticated security practices of anywhere. But the incident in Manchester, he said, shows that whenever thousands of people gather at one place, it create targets that are difficult to protect.
"Even if you harden the perimeters, they will hit at whatever choke points exist," he said. "So there is always somewhere to hit."