HOUSTON -- Police are looking for witnesses who may have seen a man who killed two people at a convenience store, KPRC Local 2 reported Friday.

Houston police said Shahzad Anwer Quraishi, 57, and Mohammad Aziz Zubair, 55, were shot to death at the Bestop Food Market in the 3700 block of Harrisburg at about 8:20 a.m. Wednesday.

Zubair called 911 and reported a robbery and shooting at the store, investigators said. He provided a description of the attacker shortly before he died at Ben Taub Hospital, police said.

Detectives said the killer is a 21- to 22-year-old black man. He was last seen wearing a black shirt and black pants.

Witnesses said they saw a man and arguing near the store at about 8 a.m. The man was described as black with a dark complexion, in his early 20s, about 5 feet 6 inches tall and about 130 pounds. He was last seen wearing dark clothing and possibly a do-rag. The woman was described as black and in her early 30s. Police said they want to talk to them as possible witnesses.

Investigators were previously looking for a white pickup truck, which has been found. Police said it was not involved in the incident.

Anyone with information is asked to call the HPD Homicide Division at 713-308-3600 or Crime Stoppers at 713-222-TIPS.