Wael Abbas, an Egyptian blogger, told Al Jazeera: "A source told me that three cars were involved in the attack and they all fled the scene after the shooting.
"The families of the deceased were protesting in front of the morgue [on Thursday] and refused to receive the bodies of their family members, demanding that the government take action.
"Instead, the government reacted by spraying them with tear gas and water cannons to disperse them from in front of the morgue."
Amr El-Khaky, Al Jazeera's correspondent in Egypt, said the family members were later permitted to receive their dead family members.
Amgad Shehata Boutros, attending the funeral of the six Copts on Thursday, told Al Jazeera: "This is definitely not Egypt, it's more like the end of days.
"This is an attempt to create sectariansim in Nagaa Hammadi. What fault did those killed have? They were just walking out of the church, celebrating Christmas, and the next thing they knew they were being fired at. What crime did they commit?" he said.
The interior ministry said the attack in the town of Nagaa Hammadi in southern Qana province, about 65km from the famous ancient ruins of Luxor, was suspected to be in retaliation for the November rape of a Muslim girl by a Christian man in the same town.
Bishop Kirollos said he was concerned about violence on the eve of Coptic Christmas, which falls on Thursday, because of previous threats following the rape of the 12-year-old girl in November.
He got a message on his mobile phone saying: "It is your turn."
"I did nothing with it. My faithful were also receiving threats in the streets, some shouting at them: 'We will not let you have festivities'," he said.
Kirollos said he ended his Christmas Mass one hour earlier than normal because of the threats.
|The attack happened in the town of Nagaa Hammadi in southern Qena province
He said Muslim residents of Nagaa Hammadi and neighbouring villages had rioted for five days in November and torched and damaged Christian properties in the area after the rape.
"For days, I had expected something to happen on Christmas day," Kirollos said.
He said police had told him to stay home for fear of further violence.
Kirollos said he had an idea of who the attackers were, calling them "Muslim radicals".
"It is all religious now. This is a religious war about how they can finish off the Christians in Egypt," he said.
Christians, mostly Coptic, account for about 10 per cent of Egypt's 83-million predominantly Muslim population.
Maged Reda Boutros, a National Democratic Party member, told Al Jazeera: "The tension tends to rise at certain points of the year and be very peaceful at others times of the year.
"When they resolve all issues; When they feel there is justice in building [Copt] churches, then there will be peace."