On Tuesday, Iranian nuclear physicist Masoud Ali Mohammadi was killed in Tehran by what Iran state media report to be a remote-detonated bomb attached to a motorbike. He worked at Tehran University, where his field of study is said to be quantum physics, an area unrelated to Iran's nuclear program. Iran has been embroiled in internal political tension, but bombings like this are basically unheard of.

Iranian state-run media initially blamed the U.S. and Israel, both frequent targets of vilification, but the U.S. dismisses charges as "absurd." Iranian media later said that royalist groups, which support the Shah overthrown in 1979, had claimed responsibility. "Green movement" opponents of the Iranian government claim that royalists have denied the attacks. Facts are scarce and commentators are filling in the gaps with big helpings of imagination and speculation. Many questions swirl around the mysterious attack, but the two most urgent are hotly debated: Who did this and why?

  • Iran 'Losing the Intelligence War'  The Guardian's Meir Javedanfar insists the U.S. was responsible. "Since George Bush left office, many people have begun to dismiss the possibility of a US attack against Iran. Judging by today's event, the same can not be said about an intelligence war against Iran," he writes. "Setbacks for Iran's intelligence apparatus against their western counterparts are bound to weaken Tehran's hands in its dealings with the west. They show that the western intelligence community is making progress in penetrating Iran's nuclear programme."
  • Mystery Demanding Inquiry  Salon's Glenn Greenwald is careful to avoid speculation but highlights "ample evidence that the U.S. covertly provides various means of support to extremist groups which have previously carried out violent terrorist attacks inside Iran." He writes, "Whether the U.S. is involved in any way with actions like the murder of this scientist -- whether directly or through its support for Iranian extremist groups -- is genuinely unknown, but the question merits much more attention than it's likely to get," he writes.
  • Targeted By Regime For Political Views?  Both the Wall Street Journal and The Atlantic's Andrew Sullivan treat Mohammadi's support for the opposition movement as the story's most important detail. Though not described as outspokenly political, his name appeared on a list of 240 Tehran University professors who supported the opposition leader. Sullivan, in a post titled "Targeting the Scientists," writes, "Naturally, the regime is blaming the US and Israel. And that is instructive. The one card the junta has to play is the Great Satan card." None of 239 other Tehran University professors on the list, however, has been killed in this manner.
  • Another Iranian Nuke Scientist Goes Missing  Middle East blogger Neal Ungerleider points out that "strange things have a way of happening to people involved with people in Iran’s nuclear program." He ticks off a list of recent scientists who has disappeared, died mysteriously, and, in some cases, either defected or been kidnapped to the U.S. "Regarding Mohammadi, all we know is that only God and someone in Langley knows for sure."
  • Why We'll Never Know  Wired's Nathan Hodge parses the confusing and contradictory spate of news outlets, in and outside of Iran, reporting wildly conflicting things. "A partial news blackout further complicates matters. Mousavi’s supporters, for instance, describe official news outlets like Fars News Agency as 'coup news agencies' that are planting false stories to blacken the opposition." He concludes of the killer and their rational, "I wouldn’t hold my breath for an answer."