according to their own standards, the deaths were because:

1) It was the Will of Allah

2) It was an attack by Israel and/or the United States

...so either they have to admit that God punished them or they have to say that they believe Israel was behind it and will have to launch an all-out war against Israel/ U.S. (which will be the regime's end). The only other option is to admit that it was a righteous f-up and have to explain it publicly - a high price for a weak leader like Khomeini to endure. 

This is not an ideal policy dilemma for a troubled theofascist government with many powerful enemies all around them, to deal with.