What was this strange sound?

my mom called me and when i answered i couldn't hear her but there was a strange sound almost like an alien and she heard it to. i live in dallas and i was on google and there have been a lot of recent sightings in the north texas area. about 2 minutes after we heard the sound a guy came at the front door selling candies but they never come to our house and the one time they do come its after the sound. isn't that a bit of a coincidence? so do you believe in aliens and what was the sound