[r9etb]

The obvious questions include, "how much of a head start did the Saudi authorities give to the militants to aid their escape, before the police started firing their guns",

Probably none. The bad guys are obviously trying to topple the Saudi royal family. The house of Saud is wobbly about a lot of things, but this isn't one of them.

[Zeppo]

I've considered that possibility... But there remains the suspicion that the "usual suspects" may be on the receiving end of a staged attack by the Saudis for political reasons (to reassure Western governments and media, for example), rather than the actual perps.