Why did the militants in Algeria kill workers from abroad at the BP plant in January?
The original question had to be edited down. I would suggest that the primary motivation of the terrorists that took the BP Gas Plant in Algeria in January was to make a statement against foreign investment in the region. The militants that took the gas plant planned their attack against this specific target precisely for the reason that it represented foreign investment in the region. In a video left behind by the militants, this becomes their stated purpose:
The Movement of the Sons of the Sahara opens the door for sacrifice... Your movement, O Youth of Algeria, is waiting for your support, to respond to injustice and aggression so the regime learns the bitterness of what is to come.
The video details how the militants believed that their mission against the BP Gas plant was one in which "Muslims fighting imperialists" is one of the refrains heard in the video. It is for this reason that the militants that took the BP plant sought to take control of it and kill workers from abroad.