The family of the man with Down syndrome who went missing for six days and was found in a Montgomery County, Maryland, Metro station is suing the company that was responsible for his care and the transit agency, saying their negligence contributed to his lengthy disappearance. Rashawn Williams, a 31-year-old nonverbal man with Down syndrome, wandered away Oct. 20, 2023, from the Residence Inn on Plum Orchard Drive in Silver Spring, which was ser…