Brock decided after the near catastrophe at the Mall today, he should go and see Shannon, instead of calling her. He needed to see where they stood, and make a decision. Today was a close call, and it made him realise that he missed her too.
It was late, but he could see a light on in Shannon's room. Climbing up to her window turned out to be harder than climbing down, but he managed it, and knocked gently on the glass.
He liked to make an entrance. Plus, he didn't want Mia finding out.