The alarm stage is also known as the fight or flight response. During the alarm stage, your brain sends an emergency signal to other parts of your body, which lets those parts know that you're in a dangerous situation. As your body mobilizes itself to react, you can choose between a fight or flight response. you'd be choosing the 'fight' response if you heard a loud noise like gunshots on a city street and , you'd be choosing the 'flight' response if you fled the scene, which according to your brain, would most likely be in your best interest.
the alarm stage, your nervous system is prepared to fight or flight. Your heart starts beating faster, which provides more blood and oxygen to your arms and legs.. If your brain suggests the fight response, you may try to fight him off and take away his knife. If your brain decides on the flight response, you may give him your money and run away, or just run away. In this case, the brain would probably suggest the flight response, leading your heart to beat faster and more blood to be pumped into your limbs, so you can get away quicker.