The eerie sight transformed a typical night sky into something out of a sci-fi movie. But local officials said there was a relatively simple explanation for the starting sight.

Residents of China’s Zhoushan city grew increasingly concerned on May 7, when the sky suddenly took on a blood-red glow.

The sky in Zhoushan, China, turned blood red on May 7, leaving residents to speculate about the cause, with some even attributing it to the start of the apocalypse. However, local officials discovered and would soon share a relatively simple explanation for the perplexing red-looking sky.

The unusual phenomenon was recorded on video by multiple residents in the area. Footage showed the sky transformed into a strange red glow on an already eerie foggy and wet night about a week before Friday the 13th.

The fog and the clouds turned out to be key to the red light’s formation. When the red light appeared in the sky, it was foggy, cloudy, and drizzling — perfect conditions for red lights on the ground to reflect off the clouds. It is suspected that the peculiar red light came from a fishing boat in the city’s harbor.

An eerie red sky was seen over much of Zhoushan after weather conditions allowed for the red lights of a ship to appear in the sky.

“When weather conditions are good, more water in the atmosphere forms aerosols which refract and scatter the light of fishing boats and create the red sky seen by the public,” said the staff of the Zhoushan Meteorological Bureau, according to The Independent.

It’s not a surprise that boats were the cause of the odd red light in Zhoushan. The city is the largest fishery in China, and it has one of the world’s busiest ports. More than 1.1 million people live in the city, which is comprised of an urbanized archipelago about a three-hour drive south of Shanghai.

Fog is an excellent refractor of light, meaning strong lights passing through it can do all sorts of weird things. Back in 2018, freezing fog helped to create stunning alien-like light pillars in parts of Wisconsin, which lit up the skies there in a variety of unusual colors.

According to ancient texts, in 1770, there was a bloody sky for nine days in many countries. In 2017, Japanese scientists published a paper in Astrophysics express, believing that the bloody sky event in 1770 was caused by large-scale solar activity.

This red glow is more something like the 1770 event or it could be a test of some sort of (space) weapon.

A number of videos were posted by the citizens of the city and there was considerable panic among them as the phenomenon is not common in the region. Many Twitter users called the red sky in China ‘beautiful’ while others went on to call it ‘apocalyptic’.