Security in the Aftermath of the Boston Marathon Explosions

The tragic bombing of Boston's marathons leaves many unanswered questions. Who orchestrated it, and for what purposes? 

Marathons are always equipped with security forces, but in this case, they were unable to stop this horrific attack.

Here to talk about the security measures marathon organizers should pursue in the aftermath of this attack, and counterrorism around large events more generally is Nick Casale, New York City's Metropolitan Transit Authority's first Deputy Director of Security for Counter Terrorism.
The tragic bombing at the Boston marathon leaves many unanswered questions. Who orchestrated it, and for what purposes? 
Marathons are always manned with security forces, but in this case, they were unable to stop this horrific attack.
New York City's Metropolitan Transit Authority's first Deputy Director of Security for Counter Terrorism, Nick Casale, discusses counterterrorism and security measures at mass gatherings.