CO-OP CITY - Police say the grandson of an 83-year-old Bronx man who was stabbed to death Thursday is a person of interest in the case.

Authorities say 37-year-old Marcus Dobson is in police custody in Sayerville, New Jersey.

They say Dobson was picked up by officers after he allegedly ran several blocks to a gas station where he carjacked a woman in the Bronx, running over her foot before driving off. 

Investigators say they are interested in interviewing him about the death of his grandfather, Reynold Dobson. Authorities say the elderly man was found unconscious by his son late Thursday evening in his Co-op City apartment. 

EMS crews pronounced him dead at the scene. 
Police say they have statements from neighbors who heard arguing coming from the victim’s apartment. 

Officials say Marcus Dobson has also had 13 prior arrests.

They say his family members have told them he may have mental health issues.