The elder, who asked that ABC News withhold his name, said there was "terror and total panic" as Boko Haram swept into Chibok on Thursday night. He described “people running helter-skelter, screaming, [and] looking for children.”
The elder told ABC News that Boko Haram rounded up "a sizable number" of school children and locked them in a church building.
Thousands fled after the militants began their assault, leaving behind the elderly, the sick and the children locked up by Boko Haram, the elder said. Residents mostly left for nearby towns but many were killed.
Bana Lawan, chairman of the Chibok local government, told The Associated Press the militants entered the town shooting from pickup trucks and motorcycles.
A significant number of Nigerian military officers left as the assault began, the elder said. Local vigilante groups attempted to defend the town, allowing residents a chance to run away.
In April, Boko Haram captured 300 schoolgirls in April. While some escaped, 219 remain missing.
Nigeria's military chief said last month that Boko Haram had agreed to a crease-fire, but the group's leader said in a video last month that the girls were "an old story," adding that they all had converted to Islam and been married off to his fighters.
The Associated Press contributed to this story.