The Telegram channel of RIA News reports that the US has claimed that it was responsible for that attack.

So far, PressTV has NOT confirmed the death of Soleimani but other media outlets have.

IF he is really dead, then the likely scenario is the following one:

BEGIN 100% SPECULATION
Trump threatened Iran, Ayatollah Ali Khamenei declared that there is nothing the US could do, and just to prove him wrong, the US murdered Soleimani. Of course, Ayatollah Ali Khamenei meant that there is nothing *effective* which the US could do. He clearly did not have a cowardly assassination in mind. As for Uncle Shmuel, he now can see that he "showed the Ayatollahs" how invincible the Empire is. And to hell with the consequences (already started).
END 100% SPECULATION.

Now back to the attack itself.