After months since officially leaving the British monarchy, Prince Harry and Meghan Markle have experienced milestones and unforgettable events in the United States.

However, that included a terrifying earthquake that rocked Los Angeles last Thursday morning. 

According to multiple sites, the Duke of Sussex was "left shaken" by the 4.2-magnitude earthquake, just hours after he delivered an opening speech at a virtual global summit for his ecotourism project Travalyst.

Prince Harry's Early Wake-Up Call

The 35-year-old prince started to give his virtual speech for his sustainable tourism project around midnight in L.A. time. In his address, he urged the travel sector to "build back better" after being massively hit by the coronavirus pandemic. 

"And that means there's a responsibility, a responsibility we cannot avoid or dismiss, for us to reshape this industry in a way that benefits everyone and everything for decades to come," the royal prince mentioned. 

However, a few hours after his virtual speech, the father-of-one has reportedly found himself being rocked by a powerful earthquake in the Los Angeles region. 

Omid Scobie, ABC News royal contributor and author of the upcoming bombshell book "Finding Freedom: Harry and Meghan and the Making of A Modern Family," revealed that the Duke of Sussex and his family "would definitely have felt it".

"There was also a part two at around 8 am UK time and it was in the middle of that, at around approximately 4:29 am, that an earthquake struck LA. It was a magnitude 4.2 earthquake and was felt strongly by many," he mentioned in the latest episode of "The HeirPod."

The royal biographer pointed out that several celebrities took to social media to express their reaction over the earthquake. 

"We saw many celebrities talking out about it on social media. And it would no doubt have been felt by the Sussexes so I'm sure some sleep was much deserved by the Duke after that."

According to CNN, residents had an early wake-up call after the earthquake hit near Pacoima, north of Los Angeles at around 4: 30 am. It was followed by a dozen aftershocks. 

Fortunately, after conducting a ground survey, the L.A. fire Department found no injuries or damage caused by the incident. 

Celebrities Left "Shookt" Over The 4.2 Magnitude Earthquake

Since L.A. is considered a celebrity hotspot, Hollywood A-listers and prominent personalities were left shaken as they ranted on Twitter. 

Reality star and Good American founder Khloe Kardashian wrote": "Oh man!! Wow, that felt much bigger than a 4.5 #earthquake. So scary! Sneakers and my flashlight by my bed."

American Idol winner and singer-songwriter Kelly Clarkson shared how her son reacted during the earthquake. She also expressed her relief that she and her kids are safe. 

"My children are in my arms and we are awake too early because of that earthquake but now they're discussing how their ninja skills would totally help in this time," wrote Clarkson. "I'm just happy they're more interested and curious about it and less scared. Hallelujah!"

READ MORE: Ellen DeGeneres NOT Canceled: 'Nobody Is Going Off the Air'