Maryland Department of General Services issued the following announcement on Aug. 26.
Governor Larry Hogan ordered the Maryland State Flag lowered to half-staff effective immediately and returned to full-staff at sunset on the day of interment (date not yet known). This action is in honor of United States Senator John McCain who passed away on Saturday, August 25, 2018. Per United States Code, the United States Flag will return to full-staff at sunset on the day after death, today, August 26, 2018, as stated in the previous notification.
Original source can be found here.