Four people were killed in a late-night attack by Muslim insurgents on a military outpost in Thailand's violence-wracked south, authorities said Wednesday, as dramatic footage emerged showing security forces diving for cover from a hail of gunfire and a grenade blast.The attack comes as anger snowballs over the case of a Muslim rebel suspect who was left in a critical condition after spending several hours in a notorious army interrogation unit. The 15-year conflict in the Malay