St. Louis County Police Chief Jon Belmar became the target.

In the dark hours leading into Tuesday morning, someone posted a photo of Belmar’s house on Twitter. Then his home address and telephone number.

By afternoon, eerie photos started to circulate on social media. A picture reportedly of Belmar and his wife with the caption: “Nice photo, Jon. Your wife actually looks good for her age. Have you had enough?” A picture allegedly inside his home of someone sleeping on the couch that read, “He sees you when you sleep, he knows when you’re awake.” And then one apparently of his wife and daughter.

Days after 18-year-old Michael Brown was shot and killed by a police officer in Ferguson, Mo. — and hours after rioting and looting erupted in response — an invisible insurgency associated with the hacking collective Anonymous threatened to wage a war of its own, telling police, “we are watching you very closely.”

Anonymous, a loosely organized global network of activists and hackers, has a history of targeting large corporations and governments in the wake of what it deems injustice. Its targets have included everyone from companies such as VISA, MasterCard and PayPal after they prohibited donations to WikiLeaks to the Israeli government in retaliation for its military intervention in Gaza. Amid this week’s mayhem in Ferguson, a group claiming to be associated with Anonymous set up a Web site to organize cyberprotests as well as a Twitter account. It released a video and put out a press release, in part addressing police:

If you abuse, harass — or harm in any way the protesters in Ferguson we will take every Web-based asset of your departments and governments off line. That is not a threat, it is a promise. If you attack the protesters, we will attack every server and computer you have. We will dox and release the personal information on every single member of the Ferguson Police Department, as well as any other jurisdiction that participates in the abuse. We will seize all your databases and E-Mail spools and dump them on the Internet. This is your only warning.

Then, apparently unhappy with the government’s response, it made good on its word.

The Internet crashed at City Hall. E-mail systems were hit. Phones died. City officials told the St. Louis Post-Dispatch a flood of traffic targeting the city’s site “just kept coming.”

On Tuesday afternoon, Anonymous took credit. The hacktivists had done this before, perhaps most notably in Albuquerque, where riots broke out in March over the police’s involvement in 37 shootings, 23 of them fatal, since 2010 — particularly the killing of a homeless man.

Now Belmar was the one in the crosshairs. At least one hacker trolled the Internet to find information on him, the Post-Dispatch reported, in retaliation for not disclosing the name of the officer who killed Brown. Authorities decided not to identify the officer because of threats made on social media. Anonymous said Tuesday it knew the name of the shooter and was making sure it had the right person before identifying him, tweeting, “Everyone be patient, we don’t want to be wrong.”

Then tweets once directed at Belmar turned to his daughter, CBC St. Louis reported, stating “Jon Belmar, if you don’t release the officer’s name, we’re releasing your daughter’s info. You have one hour.”

Then:

Anonymous eventually gave up — and it’s not clear why. As of early Wednesday morning, the group had not released the officer’s name.

Many Twitterers praised the hackers throughout the day Tuesday. Still, some called them out — particularly in posts about Belmar’s family — saying: “This. Is. Creepy.”; “Do you really think that officer went out to kill someone?” and “Dear God.”

Anonymous even seemed to show remorse.

Belmar declined comment to the Post-Dispatch, the newspaper reported.

Early Wednesday, an Anonymous group tweeted that it has obtained emergency response audio from the Brown shooting and will release the files “in the very near future.”