Megan asks the driving instructor whether she can borrow Charlie for a minute and the instructor tells her to take the afternoon. A few minutes later, whilst Charlie and Megan are talking, the instructor tells Charlie that he's up (despite being told earlier that he was finished).
Charlie's driving instructor is trying to get him to do too many things at once. When teaching a student new skills (like pursuit driving) the instructor should only add new items after the current skill is mastered. Here he should first have Charlie master high performance driving before asking him to try to handle the radio or any other job.
The knife the assassin uses is already covered in blood before she stabs the agent watching Robin.