If you yell “fire” in a crowded theater and it results in deaths and/or injuries, you will not be charged with a violation of the First Amendment.
True, wreckless endangerment, or willful endangerment resulting in death/injury. The first amendment will not be a viable defense unless you can prove that you perceived a threat of fire that led to your yelling fire in said crowded theater even when there wasn’t one (there’s a slippery slope here about depraved mind and perceived threat).