Brig. Gen. Yoav Mordechai, a spokesman for the Israel Defense Forces, said on his Facebook page Wednesday: "I have no idea who targeted the Iranian scientist but I certainly don't shed a tear."
Stratfor points out that this is the fifth successful assassination of an Iranian nuclear scientist in as many years. Additionally, according to Stratfor,
Beyond continuing a trend in assassinations, Ahmadi-Roshan's death revealed that the Iranians could be pursuing a method of uranium enrichment other than centrifuges. There are two main methods of uranium enrichment: gas centrifuges and gas diffusion. Al Jazeera reported that Ahmadi-Roshan was in charge of a project working on polymer membranes, which are necessary for gas diffusion but not for centrifuges. ...
Go to the link for the full article.
Tom the Redhunter has a valuable roundup of related events.
The MO is the similar in the targeted assassinations; two men on a motorcycle drive up next to the car while in traffic, the man on the back of the bike attaches a magnetic bomb to the car, they speed off, and a few seconds later the bomb explodes and the man inside is killed.
Iran is warning of a "cross-border, cross-regional strategy for striking back" according to the Jerusalem Post article.