Multiple things, simultaneously.
You get an alert through the app — immediate push notification with video. If you have smart lights connected, they illuminate the area. If you have speakers, they can play sounds or pre-recorded messages. scOS removes darkness and surprise, the two things criminals depend on.
Meanwhile, the system continues tracking. If the threat moves to another camera's view, scOS follows. It builds a complete picture of what's happening across your property.
All of this happens automatically. You're informed, but you don't have to do anything unless you want to.