Amid reports of an "active shooter" on campus Monday, Stevenson University students threw their desks against the classroom door, then prayed with near-strangers under computer carts.
Just three days later, elementary and middle school students at KIPP charter schools in Baltimore were hiding with their teachers in a classroom, while police searched the building for a gunman and hundreds of parents rushed to a nearby school to wait anxiously for word about their children.
There was no real danger to students or teachers in either incident. At Stevenson, someone had seen kids with a pellet gun hunting near the wooded campus. At the KIPP schools, a child saw a man with a photographer's tripod and thought it was a gun.
But in these times, when the names of schools from Columbine to Sandy Hook to Perry Hall have come to stand for unimaginable acts of violence, the public has a heightened sense of fear and vigilance, and a feeling that perhaps schoolhouses aren't safe places.
"Our shared cultural experience now includes such traumatic incidents," said Davis Shingleton, a psychiatrist at Hannah More School in Reisterstown. "We have to face reality, and the reality is that these things have occurred and could occur. That knowledge causes anxiety and hypervigilance, which must be managed."
Some students and parents criticize school officials for overreacting by sending alarming messages that turned out to be unfounded or for not sending messages until hours into the event. But safety experts and police say it is appropriate for schools and police to react quickly, as they did in both these cases.
"I think anytime in the months after a high-profile national tragedy, there's always heightened awareness, heightened sensitivity erring on the side of safety," said Kenneth Trump, president of the National School Safety and Security Services in Cleveland. "Oftentimes we see overreaction. You see that heightened response. That's OK. You want people to respond. We want threats to be treated seriously."
Baltimore police Commissioner Anthony W. Batts said that about 9 a.m. Thursday, school police received a report of an armed person on the KIPP school grounds in Northwest Baltimore. He said he is glad the students made the report.
"They saw something they misconstrued or thought was something of danger. They did the right thing: They reported it and we responded to it. And I don't think anything has gone wrong here. I think everything has gone very well," Batts said.
What students had seen was entirely innocent. Two University of Maryland, College Park journalism students had brought a tripod to the KIPP campus to record video for a class. They had permission from both the school and the school system to be on campus, according to Lucy Dalglish, dean of the Philip Merrill College of Journalism at College Park. City police confirmed that a man with a tripod was mistaken for a gunman.
Tamaya Evans, a KIPP sixth-grader, thought she was just practicing a drill when the school went on lockdown. She and nearly every student in the nation learns to lock the door, push desks in front of the door, and hide with their classmates and teacher.
Tamaya said she and 26 classmates moved to the back of the room. The students sat for more than an hour and a half, passing the time by thumb-wrestling and playing quiet games under the supervision of their teacher.
"At first it was like, 'This isn't real,'" Tamaya said. "'This isn't really happening or they would say something on the intercom.'"
Then, as the wait grew longer and longer, "reality kicked in," the 12-year-old said.
"I was scared; I was crying," she said. "I started thinking about my family. What if something happens and I don't see them?"
She remembered saying goodbye and "I love you" to her parents as she left for school Thursday morning. "But that didn't seem like enough," she added.
Hundreds of parents gathered in the parking lot at Polytechnic Institute, where KIPP brought the students. Lalishia Connor said she was in shock. She said she had a niece who attended Sandy Hook Elementary in Newtown, Conn., where a mass shooting occurred in 2012, so she knew it would be a long day.
"This is a process, and this is going to be a while," she said. "All we can do is sit and wait and pray that our babies are fine."
The lockdowns now practiced by most schools in the country help prepare students psychologically because students know they are doing what will make them feel safe during a tense situation.
Sharon Stephan, co-director of the National Center for School Mental Health at the University of Maryland, said that the anxiety and intense feelings children and parents have after a lockdown is a natural and normal response.
"Even though what happened today may not have been a real threat, it is the perception of what could happen" that can cause anxiety, she said.
Most students will bounce back to normal in a few days or weeks, she said. The best way for students to return to normal, she said, is for teachers to get students back into a routine as quickly as possible.
"It is really important that families get back into the swing of things," she said.
Some students, particularly those who have been through traumatic experiences or who already suffer from anxiety, might have stronger reactions, Stephan said.
Another tense lockdown occurred at South Carroll High School in Sykesville last month, prompted by multiple calls that threatened "shooting and chaos." Students were on lockdown for more than four hours and weren't allowed to go home until almost 7 p.m. No one was injured, and no weapons were found.
At the Poly parking lot Thursday, parents spoke on cellphones, others gathered with friends in small groups. Some wiped away tears. They said the school had not sent them any information by text, phone or email until several hours after the lockdown started. False rumors abounded, fueled by reports on social media. They heard that four shots were fired, that a student was being held hostage. None of the stories were true.
But the city school system said in a statement that "as soon as we got word from police, we immediately got in touch with our parents via phone or local and social media."
Earlier this week at Stevenson, student Abbey Neuberger said she was more alarmed by social media reports than by the college's text message that there might be a gunman on campus.
"Twitter was giving us false information and was making us more scared," Neuberger said.
As parents of students waited outside the college, texting with their children, they talked about the panic they felt traveling to the campus.
Some said they hoped Stevenson officials would review how they chose to communicate about the situation — starting with the fact that officials called the incident an "active shooter" situation, when there was no active shooting taking place.
"They're going to have to change the way they do things," said Michelle Greer as she waited for her daughter, a freshman. "We need a meeting to talk about how this was handled. I hit the parking lot and just cried."
Stevenson officials said Thursday that in the days since the lockdown, they have received positive feedback from students and parents about the prompt notification, and about the fact that they issued a strong warning based on the information reported to them.
Trump, of the National School Safety and Security Services, said school systems have to have increased communication with parents about the situation as it unfolds.
"The reality with social media is that rumors and misinformation now spread in seconds and minutes. The schools have to be ready to hit the ground running so that they are at least in the ballpark on getting out accurate information" to the community, he said.
Social media can also complicate the situation for police, said John DeCarlo, a professor at the John Jay College of Criminal Justice in New York. Police monitor social media during such situations so that if there is a report of shots being fired, officers can respond with greater intensity. Lockdowns can be inconvenient and disruptive, but, DeCarlo said, police have the responsibility to take such threats seriously.
"Until better ways come up ... we are going to see reactions like this. What choice do they have?" said DeCarlo.
Baltimore Sun reporters Colin Campbell and Justin George contributed to this article.