How does a person go from no empathy to empathy in the blink of an eye? That can happen?

Typically when people don’t have empathy, it’s because they haven’t endured something yet or they’re too stuck in their own world and themselves. Yes, empathy can be given to someone in a blink of an eye when they learn to truly care for others. It’s kind of like one of those life lesson moments when you realize something that gives you a different outlook on life.
I’ve seen it happen before.