Grenade Attack in Belgium - Authorities Don't Know Who the Attackers Are

Anyone want to go out on a limb and guess who the attackers are? Anyone? From the BBC:

Reports say several men threw grenades and fired on a crowd at a bus stop in Place Saint Lambert A gun and grenade attack in the centre of the Belgian city of Liege has killed at least two people and wounded 47 including a toddler, media say.

Witnesses say a man in his 40s threw grenades at a bus stop in Place Saint Lambert, a busy square. At least two other men are thought to be involved. Reports say one of the attackers is among the dead. Local media say another has been detained, while a third is involved in a stand-off with police.

It is not clear who the attackers are.

There are reports of a fourth man escaping the scene.

TV images showed blood splattered across the cobblestones.