Complex sentence: Hetherington was killed on 20 April 2011 while covering the front lines in the besieged city of Misrata, Libya during a mortar shell attack, which also killed photographer Chris Hondros and gravely wounded photographer Guy Martin.
Split into simpler sentences: Hetherington was killed on 20 April 2011 while covering the front lines in the besieged city of Misrata, Libya. The same attack gravely also killed photographer Chris Hondros and gravely wounded photographer Guy Martin.