(Reuters) - A college near Seattle locked down its campus for about two hours on Friday, prompting police to respond to reports of gunfire that turned out to be unfounded, according to the college and police.

The brief scare prompted the cancellation of classes and a search for a gunman at Highline College in Des Moines, Washington, that officials said came up empty.

“We are done searching the campus and have found no injuries or indications of gunshots being fired,” Kent Police Commander Jarod Kasner said in an email around midday, about two hours after the lockdown was declared.

“We have heard that it possibly could have been fireworks, and we’re looking into confirming that information,” Kasner added.

The school has about 17,000 students, according to its website.

The alarming warning came just days after a gunman entered a school in Parkland, Florida, killing 17 people and injuring others in one of the worst school shootings in U.S. history.

During the lockdown, police evacuated buildings, and people inside posted anxious messages and videos on social media about impromptu barricades, pushing chairs and tables against doors and waiting in darkness.

“I’m still in my classroom at Highline College with some students, waiting for police to evacuate us,” Stevi Costa, a teacher of English literature, wrote on Twitter during the lockdown. “This is a literal nightmare.”