Students and staff in Orono public schools raced to barricade doors with desks, metal cabinets and chains Wednesday after social media posts threatened a school shooting.

Outside the four-school campus, snowplows and police cars blocked access to roads leading to the schools. Parents sat in long lines of cars, texting with their children who were locked down inside.

Police were notified at 10:57 a.m. of threats on Twitter and Facebook that a shooting would happen at noon, Police Chief Correy Farniok said after the lockdown was lifted.

A male student was arrested about 4:15 p.m. pending felony charges of terroristic threats, Farniok said. A second male student is a “person of interest,” the chief said, but has not been arrested.

In the morning, a screenshot of the threat on Twitter made the rounds at school.

“Orono is not safe. Today at 12:00pm I will shoot up the school myself,” the tweet said, coming from a handle called “Anonymous Vector.”

Police determined that both threats originated from the high school, the chief said. The suspects were identified and both boys were found inside a classroom. Neither was armed and no guns have been found, the chief said.

“We haven’t found anything, but the investigation is ongoing,” Farniok said.

During the lockdown, students sat in their classrooms, sometimes crouched under their desks, with chairs and desks barricading the doors, according to students’ social media posts. They were kept away from the windows and doors. In one classroom, students pushed a metal cabinet toward the door to barricade it.

Miranda Waade, 18, a senior at the high school, was in her speech class on the second floor when she heard a lockdown warning.

“I freaked out a little bit,” she said.

Waade immediately called her parents, who instructed her to stay safe and aware. Her younger brother, a freshman, was on the third floor.

“I know he was really scared,” she said. “I told him, ‘If anything happens, I love you.’ ”

Waade said students were instructed to move toward the back of the classroom, away from the door and windows, and wait.

As hours went by, Waade and the other students tried to keep busy. Most were on their phones getting updates from the media; others were texting their parents. They were fed chicken tenders and fruit from the cafeteria.

About an hour before the lockdown was lifted, Waade said a police officer ran toward a nearby classroom and told everyone to be quiet.

“I think it’s really scary,” she said. “You shouldn’t have to go to school and worry if you are going to get shot. [My family and I] have been watching the news together. We’re grateful nothing happened to us.”

Cole Fischer, 14, an eighth-grader in the Intermediate School, was in choir with about 100 other students when the lockdown warning came. A substitute teacher was leading the class.

Everyone sat quietly, for a few minutes at least, looking up information on social media and Google. They had only one bathroom break and no lunch, he said.

Wednesday’s threats came after another threat Tuesday night that police found not to be credible.

Fischer said someone had hacked another student’s Facebook account and Photoshopped a photo of the student holding a gun with the caption, “I hope I don’t need to use this tomorrow.”

Fischer said his mom didn’t want him to go to school Wednesday. But after talking to the mother of that student, she gave her OK.

Elementary and middle school students were allowed to go home around 4 p.m.; high schoolers were dismissed a short time later. The 2,800-student district has four schools on a 120-acre campus on Old Crystal Bay Road and another in Maple Plain, said Superintendent Karen Orcutt. All five schools were locked down.

Police blocked streets south of Wayzata Boulevard that led to the main campus. Parents waited outside, desperate for any news updates. Others gathered at a nearby food market.

Orcutt said announcements went out on the school intercoms every 15 minutes assuring students and staff that they were safe. Officials also sent e-mail updates to teachers and staff.

“We did our best to reassure everyone throughout the day,” she said. She said classes would resume normally on Thursday with a police presence and a crisis intervention team in every building.

Orcutt said each of the district’s schools has periodic lockdown drills. “We practice for this type of event, several times a year,” she said.

With the school shooting in Parkland, Fla., just a week ago, police took the threat very seriously, Farniok said.

“We took the individual into custody in handcuffs,” he said. “We will work with the county attorney on charges. If there are federal charges [warranted], we will pursue those. We do take these seriously.”

He asked people to be wary of speculation and rumor. Social media ramped up the severity of the threat Tuesday night.

“The information going out was gossip, not fact-based,” he said. “Most of it not true and accurate. Even now, there’s a lot of information out there ... and a lot of it is not accurate.”

Orcutt offered advice to parents who might be wary of sending their children to school on Thursday.

“Listen to the police and listen to the school,” she said. “I am extremely compassionate and understand parents’ fear, but we also believe we’re safe for tomorrow. If parents do wish to keep students at home, we respect that as well.”