However, the cause of the big boom remains a mystery.
According to FOX5, the U.S. Geological Survey did not have an earthquake on record for San Diego County around 8:15 P.M.
"Heard and felt it. We thought someone was trying to break into our home," one San Diego resident wrote on Facebook. "I heard it here in Fallbrook but assumed that it was bombing on Camp Pendleton," wrote another.
It is true that Camp Pendleton did issue a noise advisory on June 3. Artillery units are scheduled to train from 6 a.m. to midnight, June 5-11," they wrote on Twitter.
However, FOX5 reports it's still unclear if the mysterious boom is related to the training at the base.
Some residents who heard it in Imperial Beach said it sounded like it was coming from the south.
San Diego Mayor Todd Gloria took to Twitter to share that he had heard the boom but also had no explanation.