it's irrelevent that he was unarmed
A charging man can cover a 25 foot distance in about one second.
Forgetting for a moment that this involved a police officer being charged by a suspect, consider this:
In the United States, stand-your-ground law states that an individual has no duty to retreat from any place they have lawful right to be and may use any level of force, including lethal, if they reasonably believe they face an imminent and immediate threat of serious bodily harm or death.