California’s Department of Justice mistakenly posted the names, addresses and birthdays of nearly 200,000 gun owners on the internet because officials didn’t follow policies or understand how to operate their website, according to an investigation released Wednesday.

The investigation, conducted by an outside law firm hired by the California Department of Justice, found that personal information for 192,000 people was downloaded 2,734 times by 507 unique IP addresses during a roughly 12-hour period in late June. All of those people had applied for a permit to carry a concealed gun.

“The improper exposure of confidential personal data by DOJ, while unacceptable, was unintentional and not connected to any nefarious purpose,” investigators wrote in their report.

An intentional breach of personal information carries more stiff fines and penalties under California law, according to Chuck Michel, an attorney and president of the California Rifle & Pistol Association. Michel said his group is preparing a class action lawsuit against the state.

“There is a lot of gaps and unanswered questions, perhaps deliberately so, and some spin on this whole notion of whether this was an intentional release or not,” he said. “This is not the end of the inquiry.”

The release of the data over the summer came shortly after the U.S. Supreme Court ruled against a New York requirement that people must provide a reason to carry a concealed gun. California has a similar requirement, and efforts to change it following the court’s ruling failed earlier this year.

Michel said the leaked data had information about judges, law enforcement personnel and domestic violence victims who had sought gun permits.

Officials at the California Department of Justice did not know about the breach until someone sent Attorney General Rob Bonta a private message on Twitter that included screenshots of the personal information that was available to download from the state’s website, the investigation said.

State officials at first thought the report was a hoax. Two unnamed employees — identified only as “Data Analyst 1″ and “Research Center Director” — investigated and mistakenly assured everyone that no personal information was publicly available.

Meanwhile, the website crashed because so many people were trying to download the data. Another group of state officials worked to bring the website back online, unaware of the data breach. They got the website working again at about 9:30 p.m., which included the personal information ready for download.

State officials would not disable the website until about noon the next day. By then, the information had already been downloaded thousands of times.

State officials thought they were providing anonymous information in the aggregate for research and media requests about the use of guns in California. But the employee who created the website included several datasets that contained personal information.

Investigators found that no one — not the employee who compiled the data or the officials that supervised the employee — knew the proper security settings to prevent the data from being made available for download by the public.

“This was more than an exposure of data, it was a breach of trust that falls far short of my expectations and the expectations Californians have of our department,” Bonta, the attorney general, said in a news release. “I remain deeply angered that this incident occurred and extend my deepest apologies on behalf of the Department of Justice to those who were affected.”

Other information was also mistakenly released, including data from firearms safety certificates, dealer record of sale and the state’s assault weapons registry. That data included dates of birth, gender and driver’s license numbers for more than 2 million people and 8.7 million gun transactions. But investigators said there wasn’t enough information in those datasets to identify anyone.

Investigators recommended more training and planning for state officials, including a review and update of policies and procedures.

“This failure requires immediate correction, which is why we are implementing all of the recommendations from this independent report,” Bonta said.