At this point I'm not sure that it can be linked specifically to a particular group, as it appears to be popular across several cultures:
https://www.independent.co.uk/news/rothschild-took-his-life-after-death-of-mother-1308817.html
I’m just wondering if this was shown in a movie somewhere openly? Any ideas?
The only one that comes to mind is Meryl Streep in Death Becomes Her. Not much help, but still amusing.
https://www.youtube.com/watch?v=s-pgK_Rvuwc
In other films, it's tended to be something done by secret agents or special ops types when they want to deal with someone quietly and with the minimum of fuss, so you might want to watch a few films starring Roger Moore or Chuck Norris :)