Nothing confirmed yet, but its usually hand grenades.
It probably is because Sweden has taken on much more immigrants, to the point where the percentage of Swedish residents born outside Sweden is 3x higher than in Norway and Denmark. This has probably overloaded the capacity of the social security system, and has lead to a greater extent of neighbourhoods where almost every older adult is a poor first-generation immigrant.
The problem is cultural, not economical. The Swedish state has, following a decision pushed by Olof Palme on Sweden having to become 'a multicultural state like the United States of America where Swedish culture is no longer the single dominant one' followed a policy to not only allow but encourage migrants to not integrate or assimilate into Swedish culture but to keep and strengthen their own, paid for largely by the Swedish state through subsidies for ethnically segregated cultural organisations. This has led to the establishment of ethnically segregated areas in many of the larger cities with names like 'lilla Mogadishu' (little Mogadishu), 'lilla Kabul', 'lilla Bagdad' and more. It has led to objectively unexplainable situations where a regime-supporting Eritrean cultural festival is organised in Stockholm by "refugees" from the same regime which then attracts opponents to the regime from all over Europe who come there to make war on those same regime-supporting "refugees" [1]. It has led to parts of Göteborg - the second largest city in Sweden - being under the virtual control of the Ali Khan clan [2] with members erecting road blocks to keep out authorities, somewhat comparable to the way road blocks were erected in Portland OR but far more established than those temporary eruptions of anarchy.
Sweden is now a cauldron bubbling with different factions - Afghans, Somalians, Moroccans, Iraqi, Syrians, Turks, Lebanese, Ugandans, Eritreans and more - striving for dominance in different types of organised crime. The multicultural 'experiment' has failed spectacularly and disastrously as was foreseen by many but which was not to be spoken of in fear of being labelled a 'racist' or 'nazi'. This labelling still continues and the denial still prevails but the subject has become more approachable due to the fact that the results of this failure are clearly and undeniably visible for anyone to see. What remains is to find a solution for the problems caused by the near half century of mismanagement and misdirection which keeps those aspects of Swedish culture and society which made it successful and worthy of emulation but does away with the ideologically driven mistakes. Given that the political party most (but certainly not solely) responsible for these failures - Socialdemokraterna or "the social democrats" - is and has for a long time being the largest and most dominant party combined with the fact that political parties in general and this party in particular are not known for admitting to past mistakes it remains to be seen whether and if so to what extent this will happen.
[1] https://www.tv4.se/artikel/3qmMWIhaUax7HuAl2mQxOF/kaos-vid-j... an [2] https://sv.wikipedia.org/wiki/Ali_Khan-klanen
Context for others: Sweden has no language, income, employment, or skills requirement <https://www.migrationsverket.se/English/Private-individuals/...> for obtaining citizenship.
In completely unrelated news, Arabic is now the second most spoken language in Sweden <https://digitaledition.chicagotribune.com/tribune/article_po...>.
>Sweden is now a cauldron bubbling with different factions - Afghans, Somalians, Moroccans, Iraqi, Syrians, Turks, Lebanese, Ugandans, Eritreans and more - striving for dominance in different types of organised crime.
https://en.wikipedia.org/wiki/List_of_grenade_attacks_in_Swe...
>The multicultural 'experiment' has failed spectacularly and disastrously as was foreseen by many but which was not to be spoken of in fear of being labelled a 'racist' or 'nazi'.
SWEDEN YES <https://knowyourmeme.com/memes/sweden-yes>
For the longest time only the parties I didn't want to vote for could talk about it.
...and therein lies the rub. Assuming you did vote you gave your vote to just those parties which did all they could to promulgate the problem by castigating anyone who dared to speak about migration in anything but a positive way as 'racists' or 'nazis'.
The only reason we can talk about it now is that those parties - or rather that party, only Sverigedemokraterna (the "national-conservative" party, their program resembles that of the social democrats of the early 60's from before Olof Palme) has been steadfast in their position with Moderaterna (the "classically liberal" party) having been one of the instigators of the current problems through Fredrik Reinfeldt's (prime minister of Sweden from 2006 to 2014) deal with Miljöpartiet (the "green party" which has been far more active in promoting migration and related activism than they have been for their original environmental goals) to "open the borders" in 2014 to "punish the country for having voted Sverigedemokraterna into the parliament". That same prime minister claimed that "Ursvenskt är bara barbariet. Resten av utvecklingen har kommit utifrån" [1] ("purely Swedish is only barbarism, the rest of development has come from the outside") - with a prime minister who thinks such about the country he is supposed to lead it comes as no surprise that he made things worse rather than better.
I'm a migrant to Sweden myself, having moved there from the Netherlands in 2002. I was surprised by the fact that Sweden had a real-life national socialist party, something which would not be possible in the Netherlands. No, it was not Sverigedemokraterna but Nationalsocialistisk Front which later changed its name into Svenskarnas Parti before they gave the ghost a few years later. Now there is something called Nordiska Motståndsrörelse (Northern Resistance movement) which seems to fill the gap. What soon became clear is that those parties did exist but that they were the absolute fringe and never attracted more than a few hundred people, were not taken seriously by nearly everyone and were mostly dangerous for their own in-crowd due to incessant infighting. The only real function these parties had and have seems to be to function as a foil for the likes of EXPO (a self-proclaimed anti-nazi/anti-racist group which may have started out that way but for many decades is more aptly described as a left-wing propaganda organisation, their research wing proudly describes itself as "Swedens STASI") and the propaganda arms of several "progressive" parties to portray Sweden as having a large problem with "nazis" and "racists". This stood and stands in complete opposition to the facts which, at least until recently, showed Sweden as one of the most tolerant and open countries in the world. This tolerance and openness having been abused past the breaking point finally seems to permeate the masses which makes the scare tactics - "skrämselpropaganda" for another fine Swedish word to try to pronounce for all you linguaphobes out there - less effective and has started to make it possible to discuss problems related to migration and integration/assimilation without immediately (or at least "effectively", the accusations are still made but they don't tend to stick as well as they did before) being shot down as a 'racist' or 'nazi'.
[1] https://www.dn.se/nyheter/politik/reinfeldt-det-ursvenska-ar...
It wasn't helped by the fact that hand grenades were classed as illegal fireworks up until like 2017, and fairly risk free to smuggle into the country.
Whether or not you think they should be legal is completely beside that point of them being the primary cause, which you pivoted away from. Likely because its hard to support.
You may remove either component, and the calamity would not have transpired.
You have it backwards.
Norway and Sweden has been - and is - flush with weapons and have been for decades.
When I grew up at least two of my neighbors had complete G3s and lots of ammo stashed in their house. There were tens of thousands of these stored in homes everywhere as part of terrestrial defense forces (Heimevernet).
This wasn't a drought. It was totally unproblematic. Even if sometimes people got angry and sparks flew things didn't explode.
Because guns aren't explosive.
Something else has happened that has made the situation dangerous.