PORTLAND – Cumberland County sheriff’s investigators are reviewing an apparent drug overdose by a 22-year-old jail inmate being held on attempted murder charges for shooting at two police officers in South Portland.

Cumberland County Jail officials said Terrell Dubois was found unresponsive in his maximum-security cell on New Year’s Day.

After Dubois was taken to a hospital, officials said a toxicology screen indicated he may have overdosed on an anti-psychotic medication he was on.

Jail officials are trying to determine how he got enough of the drug to cause an overdose.