Silento now stands accused of murder -- a Georgia grand jury indicted him in the shooting death of his cousin ... TMZ has learned.
According to new legal docs ... the grand jury hit the "Watch Me (Whip/Nae Nae)" rapper with 4 felony charges, including one count of malice murder and one count of felony murder.
He's was also charged with aggravated assault and gun possession during the commission of a felony.
As we reported ... cops arrested Silento in early February for allegedly murdering Frederick Rooks after an investigation into the man's death. Rooks, the rapper's cousin, was shot to death in the street on Jan. 21, and cops in DeKalb County linked Silento to the crime.
Silento's team claims he's been suffering from various mental health issues for several years.
He's still being held without bond.