Alabama Gulf Coast residents had an unusual alarm clock this morning when a loud boom could be heard for miles.

It was the sound of a space capsule returning to Earth and headed for a splashdown into the Gulf of Mexico off the coast of Pensacola.

NASA’s SpaceX Dragon Endurance spacecraft, with four astronauts on board, made its descent over Mobile and Baldwin counties around 4:40 a.m., leaving the loud boom behind. The crew made its overnight descent over the heartland of the U.S. following an 18-1/2 month stay in space.

“I thought someone was upstairs and dropped something heavy,” wrote one person on a Daphne Facebook page.

“Dogs started freaking out and my poor husband woke up to me freaking out thinking something exploded,” added a Fairhope resident on social media.

The crew aboard the Dragon “Endurance” had its touchdown south of Pensacola, around 4:47 a.m., closing out its six month mission spanning 3,184 orbits and 84.4 million miles, according to CBS News.

The crew included commander Jasmin Moghbeli, European Space Agency astronaut Andreas Mogensen, Japanese flier Satoshi Furukawa and cosmonaut Konstantin Borisov.

The trip from home too approximately 18-1/2 hours and began Monday when Moghbeli and her Crew 7 colleagues undocked from the International Space Station.

According to CBS, 50 minutes after splashdown, the astronauts were carried out one by one and placed on stretchers before being rolled inside for initial medical checks as they began re-adapting to gravity after six-and-a-half months in weightlessness. The stretchers were normal for returning long-duration station fliers and all four appeared healthy and in good spirits, the news outlet reports.

Fifty minutes after splashdown, the astronauts were carried out one by one and placed on stretchers before being rolled inside for initial medical checks as they began re-adapting to gravity after six-and-a-half months in weightlessness, according to CBS. All four appeared to be in good spirits.