SAN DIEGO —  Many San Diegans took to social media Friday morning in search of an explanation after a mysterious boom was felt and heard across the county.

From Mission Valley to El Cajon and north to Encinitas, residents are weighing whether the noise was a sonic boom, an earthquake or possible military activity.

“This was really loud,” Todd Zukowski, a Mira Mesa resident who heard two different booms, said to FOX 5. “It shook the house bad, we get the jets from Miramar, it doesn’t even come close to that.”

“I thought it was somebody walking on the roof,” another Mira Mesa resident, Patricia Villanueva, said. “I don’t know it was like a rumbling sound… scary.”

With a storm system sweeping the county, some have even questioned the possibility of thunder and lightning.

“The first time we just heard… it was like someone was knocking on our window, (so I) went and looked, nothing,” Zukowski said. “Thought maybe it was the wind… then about two minutes later, another one like twice the size of that just came… rattling a whole side of the house.”

What we do know — An earthquake can be ruled out as there were no indications of shifts in the area, according to the United States Geological Survey.

So what is this mysterious boom that has caused walls to rattle throughout the county?

FOX 5 has reached out to local law enforcement and military.

So far, a Marine lieutenant at Camp Pendleton says although he cannot confirm the cause of the recent boom, “routine live-fire training with high explosive munitions” may be heard throughout any time of the day. These explosions can be heard up to 50 miles away, according to the official.

This is a developing story. Please check back for updates.