The internet crashed at City Hall here on Tuesday morning. Ferguson’s website went dark. The phones died.

City officials didn’t say what happened — only that a flood of traffic aimed at the city hall website “just kept coming.”

But an international group of unnamed computer hackers had warned it would happen. In the hours after 18-year-old Michael Brown was shot and killed by a Ferguson police officer, the group, Anonymous, urged residents to the streets.

And the hackers vowed retribution if police harmed protesters.

“We are watching you very closely,” Anonymous’ distinctive electronic voice rasped in a video posted Monday on Twitter. “If you abuse, harass or harm the protesters in Ferguson we will take every web-based asset of your departments and federal agencies off-line.”

The hackers would also, the video continued, begin publicly releasing police officers’ personal information.

Then they did.

BREAKING D0X RT: CHIEF OF #FERGUSON POLICE, Jon Belmar - We have you now: http://t.co/VHxk7sPkXq #Anonymous (cc @OpFerguson)

— TheAnonMessage (@TheAnonMessage) August 12, 2014

Early Tuesday morning, someone posted the home address and phone number of Jon Belmar, the relatively new chief of St. Louis County police. And that was just the beginning.

The Ferguson protests have been informed, if not fueled, by a stream of moment-by-moment posts, largely on Twitter. Published instantaneously via cellphones by residents at the scene, the messages have told the world when crowds amass, when police line up, when tear gas flies.

But Anonymous hackers have reached beyond the web.

Anonymous has been operating for nearly a decade. It’s hard to even call it a group — those insiders who have spoken publicly about the organization describe it more in terms of each individual mission.

“It is an anarchist collective of autonomous individuals,” wrote one hacker who responded to an email from the Post-Dispatch. “Most of us are friends and work together, but we are not responsible for anything anyone else in the global collective does.”

That team member, who declined to be identified but said he was out of the country, said the core Ferguson operation is run by about a half-dozen Anonymous operatives, invited by local St. Louis activists, with thousands of “Anons” from about 75 different countries “joining in to help.”

And in the wee hours of Tuesday morning at least one of those hackers began following standard Anonymous protocol: He began scouring the Internet for personal documents regarding Chief Belmar — “doxxing” — the man Anonymous estimated was keeping the shooter’s name secret.

Just after midnight, someone posting as @TheAnonMessage linked to a web page listing Belmar’s address, phone number and the names of his wife and kids.

At 12:36 a.m., TheAnonMessage posted a photo of Belmar’s house; at 12:41, his phone number and address, and at 12:46, another missive: “... you said our threats were just hollow. See, that makes us mad.”

So Jon, Mr. chief of police, you said our threats were just hollow. See, that makes us mad. You shouldn't challenge us. #Anonymous #Ferguson

— TheAnonMessage (@TheAnonMessage) August 12, 2014

Then came the photos, all allegedly portraying his family: His son, asleep on a couch. His wife and daughter, arm-in-arm. He and his wife, together. “Nice photo, Jon,” TheAnonMessage added. “Your wife actually looks good for her age.

“Have you had enough?”

Nice photo, Jon. Your wife actually looks good for her age. Have you had enough? #Ferguson pic.twitter.com/pE1SmWvuIu

— TheAnonMessage (@TheAnonMessage) August 12, 2014

Finally, at 1:34 p.m. on Tuesday, TheAnonMessage leveled an ultimatum: “Jon Belmar, if you don’t release the officer’s name, we’re releasing your daughter’s info. You have one hour.”

Then Anonymous gave up.

“We recognize that Jon Belmar has had enough damage done to him,” TheAnonMessage wrote at 12:46 p.m. “We will save the rest of our energy for the true perpetrator.”

Belmar declined to comment for this story.

©2014 the St. Louis Post-Dispatch