It’s got to be the last one.
Makes you wonder how bulky you can make some electronics before anybody notices it’s filled with C4.
It doesn’t sound like the death toll is particularly high, but for sure it’s put a lot of people out of action, and they’re going to need a job lot of prosthetic hands.
I saw unsubstantiated reports claiming there was 10-20 grams of high explosive (eg C4). Which looks pretty “right” based on the footage I looked at before remembering this would be faces of death. An energetic “explosion” coming out the side of the pager that, combined with the metal from the batteries or the interior plates of the pager, would generate a good amount of shrapnel. So high odds of death if you were looking at your pager to read the message and almost guaranteed injury and cuts otherwise. And, if you were gripping your pager on the wrong side, likely loss of fingers (like a fire cracker in the hand).
Its one reason that a big part of securing your supply chains is to actually inspect what you purchase. (Allegedly) Israel with a few hours in a warehouse overnight could swap out a LOT of pager backplates in ways that are more or less indetectable at a glance or even picking it up (20 grams is nothing). But if you were to weigh those and realize they are 20 grams heavier than all the other pagers you bought (since packaged goods are fairly consistent), that should raise a lot of red flags.
But I am not aware of even government orgs (let alone terrorist orgs) who are willing to put the effort in to do that.