I don’t think you actually know what you’re talking about. The reasonable person standard is (while technically an “objective” test) so subjective that you can’t make this call. A reasonable person could also think that what he said was just him talking shit, basically saying “fuck around and find out.” He doesn’t have to say, “I’m not going to shoot you.” It isn’t illegal to make vague threats.
Second, and the real reason I know you aren’t super familiar with the subject, is that “pressing charges” isn’t really a thing. Going to the police with the video and them saying there was no crime is “pressing charges,” or at least as much as a victim of a crime can do. He went to the police, pressed them to charge the guy with something, and they didn’t do it. The government charges people with crimes, not the victims.
Saying “I’m not going to press charges” is basically you saying “I won’t cooperate in the government’s prosecution of a crime if that person is charged with one.” If you’re the only witness to a crime like domestic violence, it’s tough to charge the person with that crime without your testimony.