We're trying to get some sort of definitive picture of what happened to Simon and Frank but it's proving difficult.

What we know is that they were filming the house of Ibrahim Al-Rayyes, a wanted terrorist killed last year, in the Suwaidi district. It seems they were shot by gunmen in a blacked-out jeep, who escaped after the shooting.

Arab News reports that "Witnesses said Gardner kept aloof from the jeep after it came under fire but the gunmen followed and fired several bullets at him. “The terrorists fled the area thinking that Gardner was dead as one shot had hit his head,” they said."

It's too early to speculate on how the incident came about but my gut feeling is that it wasn't just a random, opportunistic shooting.

For one thing, it seems extremely unlikely that a blacked-out vehicle full of gunmen just happened to stumble across Simon and Frank while they were driving around Riyadh.

Also, this picture of Frank from Saudi television suggests that other people were milling around the area at the time of the shooting -- yet only Frank and Simon, two westerners, were seriously hurt.

So were the gunmen tipped off in advance? Were Simon and Frank followed and then ambushed? We just don't know yet.