Security was high Wednesday at Gainesville High School after school officials learned a bomb and gun threat had been scrawled on a bathroom wall, authorities said.

A student found the threatening message Tuesday, and it was also posted on social media.

The words on the wall, authorities said, were: “Thursday there will be no more Gainesville High School. And I’m going to bring my gun! And kill everyone!”

In response, school officials ordered a higher police presence, brought in bomb-sniffing dogs and searched all backpacks when students arrived Wednesday, Gainesville school superintendent Marrianne Dyer said.

Authorities don’t believe there is real danger, Dyer said. “Police don’t believe it and we concur that it is a prank,” she said. “There doesn’t appear to be a serious threat. But you never know.”

Dyer said and parents were notified by phone calls and emails. “We notified parents because parents were receiving the pictures via social media and they didn’t know where (the pictures) were coming from,” she said.

“The second one said ‘we have explosives and will blow this place up,’ ” Dyer said.

School officials said attendance on Wednesday was down by 8 percent to 10 percent.

In light of incidents like the deadly Sandy Hook Elementary School shooting last December in Newtown, Conn., and the shooting in August by a heavily armed intruder at McNair Discover Learing Academy in DeKalb County, where nobody was hurt, Dyer said school officials can’t afford to take such threats lightly.

“These are the kinds of threats that we 20 years ago might not have taken seriously,” she said. “But because of the events of the past four years, we can’t ignore this.”

Gainesville Police officers working with the school used surveillance video and tips to seek suspects, Dyer said.