It later emerged that one of the dead soldiers was no ordinary border guard but the commander of Saudi Arabia’s northern border forces, Brigadier General Awdah al-Balawi. This suggests that the attack, far from being random or opportunistic, had been carefully targeted and perhaps based on inside information regarding the general’s whereabouts.
Link:http://www.theguardian.com/commentis...cal-links-isis

The wider problem:
...it is in no position to confront Isis at the ideological level. The problem here is that Isis and the Saudis’ Islamic kingdom are ideologically similar, so attempts to challenge Isis on ideological grounds risk undermining the Saudi state too.