The Markelov brothers were bad-tempered, but they were smart, or they wouldn't have been recruited by a talented special forces unit.
After the two brothers accepted Li Du's employment, they kept a low profile.
They knew that they have not earned Li Du's full trust yet, and were usually quiet and obedient. They talked little among themselves, and would only occasionally communicate with Brother Wolf and Firecracker.
They were all soldiers and had more in common.
Another night, the helicopter appeared over the mountains.
They returned to the gold cave. The helicopter slid down a rope, and the strong iron box was tied on to it. Li Du, Brother Wolf, Godzilla, and others took out the gold box and placed in the iron box.
Then the box was locked and the helicopter flew away with it.
The mountain terrain was very rugged and they would have had to use the special forces' method to get on the helicopter and climb up the rope ladder.