A third suspect has been arrested and charged with murder in the death of Shaw Middle School principal Brian Betts. Montgomery County Police say they took Deontra Q. Gray, 18, of the of the 1300 block of Southview Drive in Oxon Hill, into custody on Tuesday and charged him first degree murder, one count of armed robbery, and one count of conspiracy to commit armed robbery. Two other 18-year-olds, Sharif Tau Lancaster and Alante Saunders, were charged Monday with murder, robbery and gun charges. Betts was found shot dead in his Silver Spring home an on April 16. Police believe the three young men met Betts after speaking with him on a phone sex chat line, and then showed up to rob him.