On Tuesday, Melissa Harris was on the phone at home when she heard a strange sound, according to CBC News. She captured the booming on video, and eventually posted it to YouTube. (Watch above.)

“In the moment I had goosebumps on my arm,” Harris tells the outlet.

Two days later, another resident, Katherine Wookey, recorded similar sounds that started up while she was having her morning coffee, reports Global News.

“It had a science fiction feel to it,” she told the outlet. “It was eerie.”

Wookey also happened to capture similar ear-shattering sounds in 2013. (Listen below.)

Many residents offered up their theories for the unnerving sounds from ranging from aliens to pranks, and even the second coming.

At the time, the City of Terrace said on their Facebook page that the booming was caused by a grader blade being used nearby.

The city doesn’t have an explanation yet for the latest audio mystery, according to Global.