I might be wrong but the shooter violated that rule too in addition to committing murder, which to newsweak seems inconsequential.
Keep in mind, the US Pravda media thinks rules are laws anymore. Only a silly wabbit would think rules are not optional.
They actually believe if someone says “No firearms in store” that that is a law. It may be in some States, but not everywhere. They would know that if they did their homework instead of lecturing people when they have no clue what they are talking about.