I don't think its a mortar, the explosion is far too small. A mortar shell would also be too heavy for a drone, and it seems to have at least 2 on board.
This looks more like a custom made IED, that has perhaps 30-50g explosive or so. At close distance like inside a car, mixed with some nuts and bolts, thats bad enough. The IRA used to use them in Northern Ireland in the 70s. Like in a box of matches or cigarettes, that explodes when you pick it up, placed in a pub as if its "forgotten".