Police say that 19 people have been killed and another 50 injured after an explosion at the Manchester Arena in northern England, where U.S. pop star Ariana Grande was giving a concert. 6 F8 U+ T& a: d4 N) Z3 C" L 3 y: H5 [ @# ]6 v) ^They say they are treating it as a "terrorist incident" as they investigate.