It has been my experience, that when the subject is the least little bit technical, the news media fail to get the details correct more often than not. The reporter in this case gets points for actually calling the machine an "excavator", rather than a "bulldozer". (That is, of course, if it
was an excavator, and not a rubber-tired backhoe, or a loader that had just switched from forks to bucket, or... You get the picture.)
Now, whether that incorrect reporting is due to the reporter being technically ill-informed, whoever gave the information to the media having "dumbed-down" the information so the media can digest it, or a well informed reporter dumbing down the information so the general public can digest it, it doesn't matter. Never take for granted the technical details you read in the news.
Was it truly a case of the pin not being properly in place?
I've used one mini-ex where the manual quick coupler engaged the upper bucket pin, and the bucket was retained by inserting
one pin in back, so the statement saying "
the pin which was supposed to stop the bucket coming off the excavator arm was not in place", could be correct.
The above having been said, my own educated guess would be that it was a quick coupler, and either the operator failed to engage it, or more likely, failed to engage it properly. If the dipper is at such an angle, and the coupler is rotated such that, the bottom bucket pin isn't engaged when the coupler is closed, then as soon as the boom and dipper are raised high enough, the bucket falls off.
It always good policy to check both visually and by feel that everything is secure before going to work with an attachment you've just changed. More than once I've had to take the excavator and fish a skid loader bucket out of a trash dumpster because they'll put any warm body on a skid loader to clean up the site, and it's an easy mistake for an inexperienced operator to make. (And even a more experienced operator who's in a hurry can make a similar mistake. Don't ask me how I know.)
Very sad indeed, and the victim was probably not exprerienced enough to protect himself by being sure the operator hadn't screwed up before putting himself in harm's way.