Syrian Nuclear Scientists Assassinated...Possible Iranian Connection?

First, the headline:

Five nuclear engineers, one of them Iranian, killed in Syria- Reuters

Attack in Syria's Capital Kills 4 Nuclear Scientists- Huffington Post

While a story of Syrian government scientists/engineers being killed would normally be a bit lost in the multitude of news concerning Syria's ongoing civil war, but it's that last bit of the headline, "one of them Iranian" that has caught many observers' eye. 

Here are some the facts concerning this story that may catch your eye too:

• These engineers work at Syria's Der Al-Hadjar Nuclear Research Center, which is home to Syria only "true" research reactor, the SRR-1.
• The SRR-1 is what is called a "miniature neutron source reactor" (MNSR), which is one of the smallest of its kind in the world.
• While the reactor does uses highly-enriched uranium as its fuel (90% enriched), it uses so little fuel (just under 1 kilogram) that using this facility's current fuel or even its spent fuel (which may contain a VERY small amount of plutonium) for making nuclear weapons is not even remotely feasible.
• However, while the MNSR can't be used to actually produce nuclear weapons, it CAN be used to experiment on methods of plutonium-extraction from spent fuel and several other non-civilian experiments. 
• The IAEA (International Atomic Energy Agency) in recent years got into something of a row with the Syrian government over the possibility that experiments of these type were carried out at this facility. 
• The reports of an Iranian nuclear engineer being killed in this attack is NOT confirmed by any Iranian or Syrian government sources but is being widely reported by various news agencies.
• The area of the capital of Damascus where this attack occurred is NOT believed to be involved in any heavy fighting, so the odds of this being a random killing of government officials by "rebels" seems unlikely. 

So what is the real significance of this story?

If confirmed, why is there an Iranian nuclear engineer working at the MNSR? 

Who carried out this killing? Syrian "rebels" or operatives of the Israeli government?

All very good questions and regardless of their answers, I suspect this won't be the last we hear of Syrian nuclear-related activities...