On Dec. 13 as the attack at the Ivy League institution played out during finals week, students took to Sidechat, an anonymous, campus-specific message board used widely at U.S. colleges, for fast-flowing information in real time.

An Associated Press analysis of nearly 8,000 posts from the 36 hours after the shooting shows how social media has become central to how students navigate campus emergencies.

Fifteen minutes before the university’s first alert of an active shooter, students were already documenting the chaos. Their posts — raw, fragmented and sometimes panicked — formed a digital time capsule of how a college campus experienced a mass shooting.

As students sheltered in place, they posted while hiding under library tables, crouching in classrooms and hallways. Some comments even came from wounded students, like one posting a selfie from a hospital bed with the simple caption: #finalsweek.

Others asked urgent questions: Was there a lockdown? Where was the shooter? Was it safe to move?

It would be days before authorities identified the suspect and found him dead in New Hampshire of a self-inflicted gunshot wound, later linking him to the killing of a Massachusetts Institute of Technology professor.

Here’s a look at how the shooting unfolded.

Stream of collective consciousness

Described by Harvard Magazine as “the College’s stream of collective consciousness,” Sidechat allows anyone with a verified university email to post to a campus feed. On most days, the Brown feed is filled with complaints about dining hall food, jokes about professors and stress about exams — fleeting posts running the gamut of student life.

On the Saturday afternoon just before the shooting, a student posted about how they wished they could “play Minecraft for 60 hours straight.” Then, the posts abruptly shifted.

Crowds began pouring out of Brown’s Barus and Holley building, and someone posted at 4:06 p.m.: “Why are people running away from B&H?”

Others quickly followed. “EVERYONE TAKE COVER,” one wrote. “STAY AWAY FROM THAYER STREET NEAR MACMILLAN 2 PEOPLE JUST GOT SHOT IM BEING DEAD SERIOUS,” another user wrote at 4:10 p.m.

Dozens of frantic messages followed as students tried to fill the information gap themselves.

“so r we on lockdown or what,” one student asked.

By the time the university alert was sent at 4:21 p.m., the shooter was no longer on campus — a fact Brown officials did not yet know.

“Where would we be without Sidechat?” one student wrote.

A university spokesperson said Brown’s alert reached 20,000 people minutes after the school’s public safety officials were notified shots had been fired. Officials deliberately didn’t use sirens to avoid sending people rushing to seek shelter into harm’s way, said the spokesperson, Brian E. Clark, who added Brown commissioned two external reviews of the response with the aim of enhancing public safety and security.

Long hours of hiding

Long after the sun had set, students sheltered in dark dorm rooms and study halls. Blinds were closed. Doors were barricaded with dressers, beds and mini fridges.

“Door is locked windows are locked I’ve balanced a metal pipe thing on the handle so if anyone even tries the handle from the outside it’ll make a loud noise,” one student wrote.

Students reacted to every sound — footsteps in hallways, distant sirens, helicopters overhead. When alerts came, the vibrations and ringtones were jarring. Some feared that names of the dead would be released — and that they would recognize someone they knew.

Law enforcement moved through campus buildings, clearing them floor by floor.

A student who fled Barus and Holley asked whether anyone could text his parents to let them know he had made it out safely. Others said they had left phones behind in classrooms when they fled, unable to reach frantic loved ones. Ironically, those closest to the shooting often had the least information.

Many American students expressed emotions hovering between numbness and heartbreak.

“Just got a text from a friend I haven’t spoken to in nearly three years,” one student wrote. “Our last messages? Me checking in on her after the shooting at Michigan State.” Multiple students replied, saying they’d had similar experiences.

International students posted about parents unable to sleep on the other side of the world.

“I just want a hug from my mom,” one student wrote.

Anxiety sets in

As the hours dragged on, students struggled with basic needs. Some described urinating in trash cans or empty laundry detergent bottles because they were too afraid to leave their rooms. Others spoke of drinking to cope.

“I was on the street when it happened & suddenly I felt so scared,” one student wrote. “I ran and didn’t calm down for a while. I feel numb, tired, & about to throw up.”

Another wrote: “I’m locked inside! Haven’t eaten anything today! I’m so scared i don’t even know if I get out of this alive or dead.”

Some students posted into the early morning, more than 10 hours into the lockdown, saying they couldn’t sleep. Sidechat also documented acts of kindness, including a student going door to door with macaroni and cheese cups in a dark dorm.

Information, and its limits

Students repeatedly asked the same questions — news? sources? — and challenged one another to verify what they saw before reposting it.

“Frankly I’d rather hear misinformation than people not report stuff they’ve heard,” one student wrote.

Others pushed back, sharing a Google Doc that would grow to 28 pages where students could find the most updated, verified information. Some posted police scanner transcriptions or warned against relying on artificial intelligence summaries of the developing situation. Professors — who rarely post on the app — joined the feed, urging caution and offering reassurance.

“If you’re talking about the active situation please add a source!!!” one student wrote.

But “reliable information,” students noted, often arrived with a delay.

Within about 30 minutes of the shooting, posts incorrectly claimed the shooter had been caught. Reports of more gunshots — later proven false — continued into the night and the next day, fueling fear and frustration. Asked one student, what are police doing “RIGHT NOW”?

Replies came quickly.

“They are trying their best,” one person responded. “Be grateful,” another added. “They are putting their lives in danger at this moment for us to be safe.”

A campus changed

Students awoke Sunday to a campus they no longer recognized. It had snowed overnight — the first snowfall of the academic year.

In post after post, students called the sight unsettling. What was usually a celebration felt instead like confirmation something had irrevocably shifted.

“It truly hurt seeing the flakes fall this morning, beautiful and tragic,” one student wrote.

Even as the lockdown lifted, many said they were unsure what to do — where they could go, whether dining halls were open, whether it was safe to move.

“What do I do rn?” one student posted. “I’m losing my mind.”

Students walked through fresh snow in a daze, heading to blood donation centers. Others noticed flowers being placed at the campus gates and outside Barus and Holley.

Many mourned not only the two students killed, but the innocence they felt had been stripped from their campus.

“Will never see the first snow of the season and not think about those two,” one student wrote.

With the lockdown ended, students returned to their dorms as Sidechat continued to fill with grief and reflection. Many said Brown no longer felt the same.

“Snow will always be bloody for me,” one person posted.