A massive Bay Area law enforcement sting operation that's been two years in the making had it's D-Day on Tuesday, and now the public is learning what it was all about. Operation Cold Day, which was a coordinated effort of the SFPD, CHP, ATF (Bureau of Alcohol, Tobacco, Firearms and Explosives), and the police departments of Redwood City, San Bruno, and Daly City, culminated in the arrests of 75 individuals, the most ever in ATF history in a single sting. Charges included possession of stolen or illegal weapons, narcotics and methamphetamine possession with the intent to distribute, convicted felons in possession of weapons, and engaging in the unlicensed dealing in firearms, as CBS 5 reports.

Some of the suspects arrested were part of car theft rings in Oakland and SF, according to NBC Bay Area.

A large-scale effort appeared to be underway on Tuesday involving the ATF, though at the time ABC 7 had few details about what was going on besides the execution of dozens of search warrants in the Sunnydale housing project. Twitterers had video of SFPD tactical and SWAT units in SoMa on Tuesday morning as well.

The operation continued into Wednesday and was apparently based out of a warehouse in Daly City, as ABC 7 reports, with searches and/or arrests taking place as far away as the Central Valley.

As the Chronicle explains, the operation targeted low and mid-level crimes, including drugs, guns, and car theft, and over two years yielded 115 arrest warrants.

District Attorney George Gascon spoke at a news conference Thursday explaining the name of the operation, which had to do with the coordination of local, state, and federal agencies. "Early on some folks made some comments that it would be a cold day in you know where before an operation like this would come together," he said. "Law enforcement is at its best when we all come together to enhance public safety," he said.

Gascon further told the Chron that the operation grew "piecemeal" out of an investigation into a rash of Zipcar thefts around May 2015 — you may recall the story of this one serial Zipcar thief who was a part of that, Nicole Dipo.

U.S. Attorney Brian Stretch noted at the news conference that the targeting of individuals who were not wanted for violent crime was on purpose — this was an effort to curtail violence before it starts by getting weapons off the streets.

"The safety of the public is at the core of ATF’s mission and we stand at the front line eradicating violent crime from our streets," said special agent in charge of the ATF San Francisco field office Jill Snyder. "One firearm in the hands of a gang member or prohibited person is one firearm too many."

"Gun violence has negatively impacted the lives of far too many people in San Francisco,” said SFPD Chief Scott, per CBS 5. "This type of violence is more likely to happen when guns are in the hands of individuals willing to obtain and/or use them illegally."