It's too late to apologise.

为什么人一定要有事情发生才会知道事情的严重性？一但事情发生之后，已经太迟了。没有办法挽救。

And instead of doing/saying something to make the person stay, that someone has to be even meaner. Doesn't he realise the seriousness of the outcome?

One tends to take things for granted and continues to be mean to another.

Of course the above doesn't apply to me.