How a thing like this could have happened? ... and Jack was standing there, stunned and stupid, trying to understand how a thing like this could have happened. Source:The Shining Context: Jack lost his temper when he saw his son ruined part of his manuscript and in anger he broke his son's arm. But after that, he regretted doing so. Hi. Can we say "could have happened" and "could happen" interchangeably because this thing has just happened not long ago? Or in this case we should stick to "could have happened" because "breaking his son's arm" is an one-off event which has finished in the past? Thank you.