In the part where Snake finds the kids in a cell offering diamonds in exchange for their freedom, snake shoots at a bucket and Kaz says "it's on recording", what was the purpose of that?
He does this to trick the contractor.
Snake and his group are mercenaries. He was hired to take out the former Mbele soldiers. The contractor failed to mention that some of them are children.
Snake isn't really the guy who kills children, but he needs the money, so he decided to deceive the contractor by recording the fake execution.