Parents said they had no faith in authorities to return their kidnapped girls and would follow them into a forest where police believes they are being held.
Although the government says it's negotiating with the gunmen who abducted more than 330 students,families still don't know if their children survived.
The group had been at the reserve for less than an hour when they were shot,their car set aflame and their bodies left in the sand.
The attacks,in the Monguno and Nganzai local government areas,came just days after militants killed at least 69 people in a raid on a village in a third area,Gubio.
Sources said gunmen attacked because they suspected residents of sharing information on the terror group's movements with security authorities.
Hundreds of people have been killed in the north-west of Nigeria since last year,in attacks the government attributes to'bandits'.
Most citizens of Nigeria - Africa's most populous nation and biggest economy - and Eritrea would be blocked from coming to live and work in the United States under the measure.
The extremists have defied the claims by President Muhammadu Buhari's administration that the insurgency has been crushed.
President Muhammadu Buhari's government has repeatedly said it was willing to hold talks with the group.
The Nigerian government confirmed 101 of the 110 girls seized in Dapchi on February 19 had been freed. Nigeria denied a ransom was paid for their release.