It is still a threat under the definition, but because he said "kindergarten" instead of naming a specific kindergarten I am saying it is protected speech under

It is still a threat under the definition, but because he said "kindergarten" instead of naming a specific kindergarten I am saying it is protected speech under the 1st Amendment. There are exceptions, but generally, it is not criminal to discuss committing a crime, in order to constitute a crime there usually needs to be a substantial step in furtherance of committing the crime.