With one suspect in custody, Marietta police have identified a “person of interest” in the shooting death of a 22-year-old mentally challenged man. But they aren’t sure where to find the 19-year-old, police said Thursday.

James Black is a person of interest in the Feb. 18 killing of Tomas Arriola, who was riding along in his father’s taxi when two customers requested a ride.

After the ride to the St. Augustine apartments, the two customers then robbed and assaulted Arriola and his father, who has the same name, according to police.

One suspect, Abdul Malik Griffin, 20, was arrested late Monday at a Powder Springs address and booked into the Cobb County jail, where he was being held Thursday without bond, booking records showed. He has been charged with murder, armed robbery and possession of a firearm during the commission of a crime.

On Thursday, police asked for the public’s help in locating Black.

Black has two distinct tattoos on the backs of both of his hands. The back of the right hand has the word “New” tattooed and the back of the left hand has the word “York” tattooed, according to police.

Anyone with information on Black’s whereabouts is asked to contact Crime Stoppers at 404-577-TIPS (8477).