If you’re talking about the TETRA flaw that made news recently, it’s unlikely to be related. The employee in the article is in the USA where TETRA is not widely used. Can’t rule it out without more details but from what’s written, it sounds like he had legitimate access to the information and tools through his workplace and decided to incorporate it into his hobbies. P25 is more common for encrypted voice and text over radio within US military and law enforcement agencies. It has vulnerabilities too but the reporting on those issues is a bit older so probably won’t make headlines again until something new comes out.
It makes sense that he’d have the information for military-related communications if that was part of his job (though it should have been left at work). As for the FBI and state agencies, those details could have been in the plans for Defense Support of Civil Authorities (DSCA) operations. It’s the sort of thing you can figure out ahead of time so you’re not scrambling to put it all together when the world is on fire. If they’ve rehearsed those scenarios with local and federal partners in the past, any officer worth their shiny collar would identify the need for seamless communication in order to coordinate response efforts more effectively.