From an AP article regarding the Georgia mobile home park murders:
"The chief said police are certain they know what happened, but don't know who committed the slayings or why"
Well, call off the investigation. We're "certain" as to what happened. Except who did it. Or why. Which means we can't know whether the killer is still at large. Or if there were multiple killers. Or if he (or she) (or they) may strike again.
But we're absolutely certain that 7 people were killed. We had four separate officers count the bodies, and all but one of them came up with 7.