A number of people who attended the concert have posted online to describe what they say was a lack of security at the arena. European countries such as France, UK and Germany are on high alert but they still remain vulnerable... RT talks to terrorism and security expert David Lowe.<br /><br /><br />RT LIVE http://rt.com/on-air<br /><br />Subscribe to RT! http://www.youtube.com/subscription_center?add_user=RussiaToday<br /><br />Like us on Facebook http://www.facebook.com/RTnews<br />Follow us on Twitter http://twitter.com/RT_com<br />Follow us on Instagram http://instagram.com/rt<br />Follow us on Google+ http://plus.google.com/+RT<br />Listen to us on Soundcloud: https://soundcloud.com/rttv<br /><br />RT (Russia Today) is a global news network broadcasting from Moscow and Washington studios. RT is the first news channel to break the 1 billion YouTube views benchmark.
