MARYSVILLE — Jordan Reynolds was in the school cafeteria. The sophomore didn’t see the shooting. But as soon as the shots stopped, she ran out with a bunch of classmates who hid in a small, dark room. She called her mom. Almost everyone crammed in the room was on a phone.

“Within ten minutes, I was getting texts from people who didn’t even live in Marysville but knew what happened,” she said. “It’s crazy how fast word travels.”

It’s also scary, she said.

No one in that room knew what to believe. They heard there were six students dead, then two students dead, maybe a teacher, maybe more. So much was unclear, even a few hours after Friday’s shooting as Jordan sat with her mother in the Living Room Coffee House.

The phone went off in her hand. She looked down at a text.

“She’s alive,” she breathed, finally getting word about one of the students who had been shot. “Mom, she’s alive. She’s in the hospital.”

Then she waited for the next text, the next social media update.

“You know, you just don’t know what to believe,” Reynolds said.

Minutes after the attack, students using Twitter and social media provided critical information during the school lockdown and told their parents they were OK. Others in classrooms far away from the cafeteria used it to find out why they were hiding.

By Saturday, the tools teenagers rely on offered a whirling mass of information. Facts, rumors, hearsay, feelings, opinions, even downright lies — spread throughout the weekend, causing as much disruption as clarity.

Active feeds with their own hashtags on Twitter and Instagram mourned the deaths of students who were still alive. A screenshot of a text message purported to be from someone close to one of the families spread over Twitter Saturday night. It wasn’t true.

Heather Bravine-Natterstad was attending a vigil at the New Life Foursquare Church in Marysville at the time. “In the middle of the vigil a bunch of the girls there started crying and left,” she said.

One of the counselors on scene told her the girls were reacting to word that one of the injured girls in the hospital had died.

As of Sunday morning, all four of the injured teens were still gravely wounded, but alive. Around 10 p.m. Sunday, it was announced that Gia Soriano, 14, had died.

Teresa Wenta, chief communications and marketing officer for Providence Regional Medical Center in Everett, spent the weekend debunking rumors.

“Really for the sake of the… families and loved ones, we would ask the community not to be using social media that isn’t verified,” she said.

The bad information piles up, Harborview Medical Center spokeswoman Susan Gregg said. Social media often picks up on unverified information following tragedies.

“It does create more anxiety and pain for the families dealing with it,” Gregg said.

“There’s a lot of inaccurate information. Families need to have information released when it’s appropriate for them,” she added. “They’re going through a lot.”

Both hospitals have been putting out regular advisories, to the news media and on social media sites, updating the teens’ conditions. Providence set up a website at providence.org/marysville for Soriano and Shaylee Chuckulnaskit, 14. Harborview has been tweeting updates on Andrew Fryberg, 15, and Nate Hatch, 14, at twitter.com/uwmedicine.

“How would you feel if you heard on social media that someone had died, and you were a family member and didn’t know it was true or not?” asked Marge Martin, executive director of Victim Support Services in Everett.

“To hear from another source that your loved one is dead? I can’t imagine the cruelty of someone who would do that,” Martin said. “It just creates more pain.”

Other people seem intent on piling on the pain.

Someone created a Twitter account in Jaylen Fryberg’s name to bully M-P students and post threats. A website using one victim’s name sends those who land on it to a pornography site. Someone created a video “proving” Friday’s shooting is faked; others have snatched posts and photos from the social media of all the kids involved to create lists that draw clicks they can turn into money.

For those bad actors, trolling Twitter feeds or trying to cause harm is often part of online life, especially on Twitter where anonymity is commonplace.

“Most of it seems to be focused on getting more attention to the account and getting more followers,” said Kate Starbird, an assistant professor in the University of Washington’s Department of Human Centered Design and Engineering.

Starbird’s studies focus on how people react to disasters. While rumor and misinformation predate the Internet, technological advances have sped up and expanded the reach of what used to be local and word-of-mouth rumor mills.

“It actually stems from the natural process of trying to make sense of what’s happening,” she said. “Disasters bring out a lot of pro-social behavior but they often don’t get the facts right.”