A fifth suspect has been arrested in connection with the murder of Shaw Middle School principal Brian Betts, WTOP is reporting. The Washington Post identifies the suspect as Joel Johnson, 19, of an unconfirmed address. Johnson was reportedly arrested Tuesday evening in the 100 block of Ivanhoe Street SW, and is currently being held in the D.C. Jail, awaiting extradition to Montgomery County. Johnson faces charges of one count of first-degree murder, one count of…