I reckon the police need to investigate what she says! If only check the seat number and find out who it was purchased it! I personally think that the fu**er was not on his own! He probably had others on the inside guiding him! Just my honest opinion!
It was a well timed attack, I don't think he could have got away with hanging around outside for long, concerts can drag on (I was told she sang an extra song which went over time) so he needed to know when to start walking towards the building surely, maybe waiting for a phone call from someone saying that people were leaving?
Also the i