It looks obvious

For god sake, why should they have done that? And why the extra brutality?

Egyptian soldiers killed four Sudanese refugees, beating two to death in front of horrified Israeli soldiers, an Israeli TV station reported Thursday, screening what it said was army surveillance video and interviews with the soldiers.

[...]

Israeli soldiers were sent to the scene to try to help the refugees, and at one point they got into a tug-or-war with the Egyptians, each side holding on to the Sudanese.

"We pulled one way they pulled another, they pointed their guns at us," said one of the soldiers. He said the Israelis let go for fear that the Egyptians would fire at them.

Then the Israeli soldiers said they watched helplessly as the Egyptians passed the two refugees from one to the other, beating them. "We saw them gang up on them and beat them on the ground until they stopped moving," said one soldier.

"They killed two men with their own hands and sticks and rocks," he said. "We heard them crying and screeching in pain until they died."

I simply don’t get this - the cruelty that serve nothing but itself.