Especialy when the person is clearly not a normal human given her horns. Considering this is the Marvel universe and the guy likely witnessed an evil Captain America unleashing an army of Hydra minions and super powered villains on his city barely a few months ago he really should have been a lot more carefull, personal opinions, views, temper or morals aside.
If not a mutant she could have been a Sartyr, a minor deity, a demon or something else which could overreact extremly quickly and violent to being argued with in the wrong state.
But then again there are plenty of TV shows where surveilance camera footage is shown with people are acting on their most impulsive and stupid state of mind. So it's not like this guy was particular unusual or typical just for the Marvel Universe.
Still that was clearly murder or at least manslaughter by Nature Girl and under what i think would be classified as lower motives.