Deaf Schools Take Part in National School Walkout; Stephen Hawking Passes Away at 76; Democrat Conor Lamb Had Edge in Close PA Special Election; UK PM May Expels 23 Russian Diplomats Over Nerve Agent Poisoning; Puppy Dies in Overhead Storage Bin on United Airlines Flight; Theranos Founder Elizabeth Holmes Charged with Massive Fraud; Teacher Fires Gun in Classroom on Accident, Teen Suffers Skin Wound