The shot which killed the student was said to have been fired accidentally by the officer who was guarding a local politician on a campaign trail.
The civil defence officer was arrested immediately by the police.
The incident happened on Saturday in Amassoma, Southern Ijaw Local Government Area of the state.
The victim has been identified as Obinna, a 100-level student of petrochemical engineering of the Niger Delta University.
NSCDC Commandant-General, Abdullahi Muhammadu, on Wednesday, described the incident as “unfortunate and regrettable”.
Mr Muhammadu, who said Obinna’s death would have been avoided if the officer was careful with his rifle, said the killing was a “huge loss” to the family
He assured the victim’s family of justice.
“I assure the family that the erring officer will not go unpunished. He will be sanctioned in accordance with the law, to act as a deterrent to others,” Mr Muhammadu was quoted as saying in a statement issued by the NSCDC spokesperson, Emmanuel Okeh, in Abuja.
The officer is still in detention and would be investigated, Mr Muhammadu said.
He, however, said the officer was found not to have been drunk when the incident happened.
Mr Muhammadu said the NSCDC has “zero tolerance for accidental discharge” and have given much training to its officers.
The commandant-general cautioned civil defence officers to be more professional and responsible in their duties, as “stiffer penalty will be handed down to anyone found culpable in such avoidable and life-threatening mistake”.
He said the NSCDC would assist the family in giving the late student a “befitting” burial
He prayed for the repose of the soul of the departed student.