Matt is given a jar with eight marbles, six of which are red and two of which are green. Matt then randomly draws marbles without replacement. If he selects a red marble, he puts it in the first box; similarly, he continues to place all red marbles he selects into the first box until a green marble is chosen. When a green marble is chosen, he puts the first box aside. He then selects and places red marbles in the second box until the second green marble is chosen. When the second green marble is selected, he will put the second box aside and place all remaining red marbled in a third box. After all marbles are drawn, what is the probability that each box contains two red marbles? Express your answer as a common fraction.