Aside from the risk of boring people to death, a PowerPoint presentation is usually not threatening. But as George Gascón clicked through slides in a packed auditorium at the San Francisco Hall of Justice on a January afternoon, it became clear the district attorney was offering a challenge.

The occasion was the 62-year-old's inauguration to a second term, following his uncontested re-election the past fall. Even after seven years in San Francisco, Gascón's second inauguration had a heavy Los Angeles flavor.

A refugee from Castro's Cuba, Gascón lived in L.A. for almost 40 years and spent over 20 of them in the LAPD, briefly in the running to become chief there in the early 2000s before he became the first outsider in decades to lead the San Francisco police department in 2009. He held that post for 18 months before becoming the even-more-surprising choice to succeed incoming Attorney General Kamala Harris as district attorney.

The welcome address came from Fr. Greg Boyle, a Jesuit priest famous for working with gang members in Boyle Heights in East Los Angeles, where Gascón worked as a young cop back in the 1980s, an era when L.A. saw 1,000 homicides a year. The swearing-in was performed by Cruz Reynoso, Southern California born-and-bred and the first Latino to serve on the California Supreme Court (as well as the first to be thrown off of the court by voters after reducing too many death sentences to life imprisonment).

Most of San Francisco's prominent leaders, like Mayor Ed Lee and former Mayor Willie Brown, were elsewhere, which means they missed the PowerPoint — and the obvious challenge thrown their way.

Gascón began with a slide featuring a familiar sight even to Angelenos: San Francisco in ruins after the 1906 earthquake and fire. Those days were notable for prosecutors as well as for history buffs. This was the time when an elected district attorney brought corruption charges against San Francisco's mayor and main political boss, Gascón told the room.

Municipal graft was widespread in early 20th-century America, but San Francisco was special: The city had a mayor and a Board of Supervisors so greedy they would "eat the paint off of the side of a house," in the words of one Abraham Ruef. He would know. A UC Hastings graduate who became San Francisco's version of Tammany Hall's Boss Tweed, Ruef assembled and ran San Francisco's political machine.

In 1902, Ruef installed a photogenic musician with no political experience, Eugene Schmitz, as a puppet mayor. Similarly corrupt supervisors steered city business toward Ruef and his friends, collecting their cut. Under Ruef, city officials made a killing running hustles on prize fights, gas rates, telephone service, and streetcars. Ruef invested his cut of the spoils into real estate speculation, buying property in the up-and-coming Mission District.

Everything was running smoothly — even after the 1906 earthquake leveled the city, an occasion Ruef, thinking like a developer, used to try to evict the Chinese from Chinatown — until William Langdon, the district attorney chosen by the Ruef machine, went rogue and started enforcing the law.

With help from a federal prosecutor sent by President Theodore Roosevelt to San Francisco specifically to break up the cabal, Langdon indicted both Schmitz and Ruef. Ruef did everything he could to shut down the investigation — the special prosecutor was shot in the face (he survived), and Ruef tried to have himself appointed DA (he failed) — but Ruef was convicted and eventually did time in San Quentin.

The DA had cleaned up dirty San Francisco.

"We sometimes have to hold powerful people accountable," said Gascón, front and center on the auditorium's stage. "And it does not make for a popular decision. But it's critical for democracy that we do so."

Gascón moved on with his presentation, showing slides of his prosecution rates and how he'd been trying different things — community courts, youth courts, drug courts — to fix what he has repeatedly called a "broken" criminal justice system.

Elected officials and politicos would barely notice. Gascón had issued his warning. The question was whether he could back it up.

Two weeks later, Gascón strode into a narrow, rectangular room on the Hall of Justice's third floor and faced a bank of television cameras. The day before, news had broken that a pair of fundraisers, working to retire debt from Lee's 2011 election campaign, had secured a campaign donation for Lee from a lumber company that later won a city contract.

The fundraisers — Zula Jones, a retired contract compliance officer with the city's Human Rights Commission once feted by Ed Lee as "freedom fighter of the year"; and Nazly Mohajer, an appointed Human Rights Commissioner — had been in the news for months. Transcripts from an FBI wiretap, capturing their boasts of the city's modern-day political machine — and how they learned all the tricks of laundering cash and "pay-to-play" politics from Willie Brown — had been made public in August 2015.

"You got to pay to play here," said Jones, according to the wiretap. "We do it better here than in New York."

Standing next to an FBI special agent assigned to public corruption and City Attorney Dennis Herrera, Gascón announced that he was enforcing the law. He was filing corruption charges against Jones and Mohajer (as well as a third corrupt political operative, former Lennar Urban consultant Keith Jackson, who had already pleaded guilty and been sentenced to federal prison time in a separate, much splashier case that nabbed state Sen. Leland Yee on public corruption charges and Chinatown mobster Raymond "Shrimp Boy" Chow for murder-for-hire).

Jones and Mohajer were no Ruef and Schmitz. There were no direct ties to Lee, any sitting elected officials, or to Jones' supposed mentor Brown (whom the feds had been probing without success for decades). They might have been too small for the feds to bother with. But it was definitely not a popular move at City Hall. Gascón was getting close to Lee, which meant he was getting close to some of the same people who had had a hand in his appointment.