The Al Quds Brigades website insists that it was an Israeli airstrike, and that the cowardly Zionists don't want to admit that they are breaking the supposed truce (where the Israelis don't fire but the Gazans keep shooting rockets into Israel.) They note the huge intensity of the blast and say the mujahid's body parts were all over. They also claim a huge crater that proves it came from a missile.
The photos of the car indicate that there was indeed a huge explosion, but I cannot see anything that looks like a large crater - I do see a small one on the very bottom here:
This photo shows the street was discolored but there is no hole there:
Lots of other photos at the Islamic Jihad website.