Residents along the Northern California coast were ordered Thursday morning to evacuate as quickly as possible and asked to seek higher ground afterward a magnitude 7 earthquake off the coast of Humboldt County triggered a tsunami warning.

The warning issued just before 11 a.m. warned that “a tsunami with damaging waves and strong currents is possible.”

But about an hour later the alarm was lifted.

For some, it felt like emergency whiplash. Others were confused.

However, officials say they followed proper protocol for responding to a potentially dangerous tsunami and that it was necessary to give residents enough time to get to safety.

“Time must be respected to keep people safe,” said Dave Snider, the tsunami warning coordinator at the National Tsunami Warning Center in Alaska.

“The biggest challenge with tsunamis is that we know a major event has occurred,” Snider said of the earthquake. “We don’t know if a tsunami will actually happen.”

Given the size and location of the earthquake, his team immediately took action for a possible tsunami. The first step is to issue a warning that is as targeted as possible.

Read more: A magnitude 7.0 earthquake shakes northern California, stoking concerns before the tsunami warning is lifted

“For us, there are only two ways to know that a tsunami is happening: We have the deep-sea buoys and coastal observation stations in ports and harbors – that’s all,” Snider said. “We want to beat this wave and we want people to stay away too” … before we watch this wave.”

Snider said there was initially no confirmation that a tsunami was headed for the West Coast, but all the ingredients were there. The earthquake’s proximity to the California coast made it particularly urgent to begin evacuations because if a tsunami formed, it could strike much faster than a seismic event further out to sea, he said.

“We are completely reactionary to the earthquake event,” Snider said.

After issuing a warning, his team spends the next 30 minutes to an hour trying to understand the earthquake’s “failure mechanism,” determining how it shook the Earth, confirming its strength, and checking these buoys and coastal lookouts for further signs of one to monitor growing tsunamis. All these factors confirmed the positive news: no major tsunami, no signs of danger. The warning has been lifted.

He knows the back and forth can be frustrating, but he wants people to understand that being overprepared is better than the opposite.

“The feeling out there is, ‘Nothing happened, why did I evacuate?'” Snider said. “No, you did the right thing.”…It could have moved a lot of water. We’re glad that wasn’t the case.”

Not long after the tsunami warning was lifted, Snider discovered that his team actually saw a small tsunami – measured at 5 centimeters – occur in Arena Cove, off Mendocino County.

“Something happened, something significant happened on our planet,” Snider said.

Read more: “It’s crazy.” How unsettled Northern California weathered the 7.0 magnitude earthquake and tsunami warning

For the hour that the tsunami warning remained in effect, officials in Del Norte County, Humboldt County, Mendocino County, Berkeley and San Francisco urged people on the coast to evacuate inland.

At Fort Bragg, boat owners quickly scrambled to get their boats out of the harbor.

Sirens wailed in Ferndale, signaling the necessary evacuation.

In San Francisco, firefighters drove up and down beaches shouting to people: “Evacuate the beach, tsunami warning.”

Dan Beniflah was walking his dog on the beach before firefighters arrived. He said the warning felt similar to a tsunami scare decades ago, but he remembers that “nothing ever happened.”

As was the case then, the water looked normal Thursday, he said.

But Snider urged people not to ignore such warnings – which remain quite rare – or go to the beach to watch the waves.

“Remember what it means to live in a tsunami country,” Snider said.

Staff writers Ruben Vives, Jessica Garrison and Hannah Wiley contributed to this report.

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This story originally appeared in the Los Angeles Times.