Lake Orion Police Department issued the following announcement on Dec 7.
Update:
There were no shots fired and there are no injuries at Walled Lake Central High School. We have cancelled any more police response to the high school. The investigation continues as to the source of the original 911 call.
FALSE ALARM
We received a report of shots fired at Walled Lake Central High School at 8:31 a.m. We have multiple units and other local police departments on scene. The building has been cleared.
Original source can be found here.