Sergeant O'Donnell said an agent offered $75,000 for the cocaine.
Sergeant O'Donnell said it was unclear why the mother and the teen-age girl were shot.
"It appears the area is a drug location," Sergeant O'Donnell said.
Sergeant O'Donnell said it was not known why the men fired into the group.
Sergeant O'Donnell said the boy's body had been bruised and his eyes blackened.
"Police were there at the scene, and he approached us," Sergeant O'Donnell said.
Four men are being questioned in connection with the shooting, Sergeant O'Donnell said.
Sergeant O'Donnell said the money came from private contributions.
Sergeant O'Donnell said none of the victims was seriously injured.
Sergeant O'Donnell said an autopsy would be performed to determine the exact cause of death.