>> the box office and the queue from the arena space, i was covering an event there two days ago and everybody entering the arena is patted down. so it's a public space joined to the train station, and then you get into the arena space. and you're patted down, i guess, routinely. >> we appreciate it, it helps to try to piece together what may have happened. i want to go back to shimon, what are you learning? >> reporter: just getting word here into our newsroom in washington to see that the possible cause into this explosion was a suicide bomber. three officials who have been briefed on this investigation, two u.s. officials and a western official to pamela brown all have said that right now investigators on the scene believe that a suicide bomber detonated a bomb as people were leaving the venue, which then caused all of these injuries and the deaths.