ALIQUIPPA, Pa. -- Authorities say a Beaver County drug suspect is a "person of interest" in the shooting death of a Mercer County doctor on a road trip with his wife.

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Slideshow: Doctor Shot During Turnpike Break

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Dr. Gulam Moonda, 65, of Hermitage, was killed May 13 on the Ohio Turnpike in North Royalton. A police report says he was robbed and shot by an unknown person while his car was pulled over.

Moonda's wife, Donna, 46, was not hurt.

On Monday, Pennsylvania State Police announced the arrest of Damian R. Bradford, 23, of Monaca, on misdemeanor drug-related charges and a parole violation. He was being held in the Beaver County Jail on $50,000 straight bond.

Without giving a reason, news releases from Pennsylvania and Ohio state police identify Bradford as a person of interest in Moonda's death.

According to an affidavit of probable cause, a search warrant was issued for Bradford's apartment as part of an attempt to gather evidence.

Bradford's mother, Sharon, told Channel 4 Action News that her son has been romantically involved with Donna Moonda for some time.

That allegation is also included in the affidavit, which cites a confidential source who claims that Donna Moonda rented an apartment for someone named Damian and wanted a lucrative divorce.

Sharon Bradford said her son "feels terrible that a man got killed" but is not involved in the death.

"He's just the boyfriend. She comes here to see him," Sharon Bradford said.

Damian Bradford has not been charged in connection with the Moonda case. He faces a preliminary hearing in the drug case this week.

Donna Moonda was unavailable for comment Monday.