According to prosecuting documents ... prosecutors believe the alleged witness tampering went down in October 2016 ... when XXX was initially arrested for domestic violence. He's accused of beating his then-pregnant ex-girlfriend.
Law enforcement sources tell us XXX made multiple phone calls while behind bars, which were recorded ... as all prisoner calls are. We're told evidence from those phone calls led to the new charges.
XXXTentacion is currently in jail due to the violation of his bond and the judge has revoked his phone privileges.