They talk of wanting Israel to be an Islamic state and then condemn this? They don't need proof that Jewish Israelis did this, they just want to stir up even more civil unrest. Seeing the Islamist agenda around the world, it wouldn't surprise me if an Arab threw the firecracker intentionally. Just like the deceitful Muslims clerics from Denmark who added 3 very offensive pictures to the innocuous cartoons of Mohammed, and touted them around the middle east to start the global jihad.
Aden hotel used by Yemen goverment hit by grenade (Reuters)
from the article: Israeli Arab leaders blame gov't for Nazareth church attack