In the part in peru where you fight the T-Rex, get behind those huge spikes and shoot the T-rex until it goes berserk. Then it will charge. Adrenaline dodge, then shoot his eye. It will charge right into the needled log and shatter it. Repeat this step for the other two logs. Complete the epic interactive scene for one of the most epic kills you will get in the game. Note: This will also get you an achievement. Congratulations!