rany_ parent
First thing that came to mind is that he might have been secretly working for Israel's nuclear program but this is all very speculative. It does feel plausible though given that Israel has already assassinated plenty of Iranian nuclear scientists; so there is some precedent for it.
It does sound like something Iran might to in retaliation.
There are lots of different scenarios you can conjure up. Another could be that Israel assassinated him after he refused to support their nuclear program OR to silence him.
That, OTOH, doesn't sound like something Israel would do at all.
You're right, it's only fair that we let Iranian assassins kill people in the US.