MANCHESTER, England - A witness who attended the venue in the northern English city of Manchester where US singer Ariana Grande had been performing said she felt a massive explosion as she was leaving the concert."We were making our way out and when we were right by the door there was a massive explosion and everybody was screaming," Catherine Macfarlane told Reuters."It was a huge explosion - you could feel it in your chest. It was chaotic. Everybody was running and screaming and just trying to get out of the area."