"RE: "why are you assuming he's a 'jihadist' exactly?""
I think the assumption goes something along the lines of
1) He was in poesssion of a (fake) car bomb.
2) This has no other purporse than blowing up a car and killing people nearby with shrapnel.
3) That's usually connected with terrorism.
4) The substantive majority of people slaughtering random crowds at the moment are jihadists. (replacing the IRA, and wide variety of terrorist groups funded by the soviet union during the cold war in revenge for us bankrolling and supplying the taliban and causing the soviet union to have to quit afghanistan)