Two men in wigs and sunglasses shot dead four Coptic Christians jewellery shop workers in the Egyptian capital on Wednesday in an apparent gangland-style slaying, a security official and witnesses said.
The shooting happened at around 12:30 pm (0930 GMT) in the mixed Christian-Muslim district of Zeitoun in northeast Cairo, the official said, adding that the attackers escaped without stealing anything from the shop.
Eyewitnesses told AFP that the men arrived at the shop on a motorbike, walked in and shot dead the shop's owner and three employees before driving away, in a rare act of brazen bloodshed in the capital.
"Preliminary investigations show that the motivation behind the attack could have been revenge," the official said, adding that the owner had frequent disputes with local residents.
The official had initially said the killings were the result of a drive-by shooting.
Police, who swiftly cordoned off the area, found 15 revolver shell casings at the scene, the official said.
Cairo's Zeitoun district is a famed pilgrimage site where, according to witness accounts, the Virgin Mary appeared above the Church of Saint Mary over a period of several years in the late 1960s.
The apparitions were seen by millions including Copts, Muslims, Jews and atheists.
Egypt's Copts -- the largest Christian community in the Middle East -- account for an estimated six to 10 percent of the country's 76 million inhabitants and complain of systematic discrimination and harassment.