Alien is aiming with rifle and then shot Micah. Regarding distance and Micah moving, he turned his rifle in way too wide angle.
The astrophysicist states that the signal is coming from 30 AUs (astronomical units) from Earth and that that is "beyond the edge of our system". 31 AUs from the sun would place the source of the signal just past the orbit of Neptune and not outside of the solar system.