Samira Muhammadi hopes an international investigation can “extinguish” her pain after a Pakistani bombing killed her son and hundreds of other Afghans in the capital Kabul last month.The March 16 attack hit a drug treatment centre and killed 411 people, according to Afghan officials.A United Nations source, speaking on condition of anonymity, said they had verified at least 250 killed, with more still missing.“There should be investigations on this … Like me, many mothers lost their sons,...