The News Agency of Nigeria (NAN) reports that the state Police Commissioner, Mr Garba Umar, had confirmed that eight worshippers died and 18 others were injured in the early morning attack.
"When the chaos subsided I went inside, I saw my fellow church members dead in a pool of their own blood and many others were screaming in pain", said Chukwuma Emeka, a witness.
On getting to the church, he had left and out of anger, probably, they rained bullets on worshippers in the church.
At least 12 people were killed Sunday when a gunman entered a church and opened fire in southern Nigeria, police said.
He expressed worry that the incident was tragic as innocent people were attacked over a drug war concerning two overseas based Ozubulu brothers.
He extended his heartfelt condolences to families of the victims, people and government of Anambra state, Nigeria and the Catholic Church over the sad and unfortunate incident.
He added that the remains of the dead had been deposited at Nnamdi Azikiwe University Teaching Hospital, Nnewi.
According to the priest, an unidentified man came into the Church, shot at a man, Akunwafor Ikegwuonwu, before shooting sporadically at other worshippers.
The commissioner said information available to police showed that the attacker was speaking undiluted Igbo Language at the time he was firing at worshippers.
Police officials described the incident as apparently related to a local dispute, rather than anything carried out by the radical Islamic terrorist movement Boko Haram.
He said that they later went on rampage and shot at the remaining worshippers numbering over 100.
Umar said: "From our findings, it is very clear that the person who carried the attack must be an indigene of the area".
Governor Willie Obiano has however vowed not to rest until the perpetrators of the killing are brought to justice.