Fitchburg police are trying to determine who fired the shot which sent a bullet into a house Monday morning, narrowly missing the people inside.  The incident was reported to police at about 11:15 a-m.  The stray bullet passed through an exterior wall, then through the headboard of a bed where a mother and her child were sleeping.  It was found in an interior wall.  Nobody was hit and no injuries have been reported.  Investigators say they don’t have a suspect yet.