It's understandable, if it happened in a small-medium sized airport.
But, the fact is that it happened in Seattle Tacoma Airport, the most famous airport in the state of Washington.
US authority has to take it seriously. The incident means anyone working as ground staff can operate aircraft without notifying anyone.
It's a big security hole in the United States.
Though I've heard that some small airports in the country will skip baggage inspection to reduce cost, the authority should review its policy.