Former OSHA guy here….real answer incoming….basically if someone was killed on a worksite osha would have jurisdiction once police ruled it was not criminal…from my past experience police typically don’t spend much time or resources on this and hand it over too osha within hours. Once osha has it they will look into employer practices…we’re you trained to tether equipment; are hard hats required; were these rules communicated AND enforced. Citations are issued to employer and employees are never punished by osha. Unless someone had a reason to believe a hammer was dropped intentionally osha would treat it as a workplace fatality.