When the historic Hibernia Bank building was hit by graffiti vandals in October 2013, it was one tag too many.

It was bad enough that the big, unsightly “Mike” tag contributed to the general mess and disorder that area residents have been trying to clean up for years. But the hitting of the grand old building, originally built in 1892 at Jones and Market and designated a historic landmark, triggered both anger and resolve. Enough was enough.

Graffiti has been a problem in San Francisco for decades, and the common complaint is that no one is ever caught — and if they are, they’re charged with a misdemeanor and given light punishment.

Not this time.

Earlier this month, Michael Sullivan and Jack Nelson, both prolific, unrepentant taggers, pleaded guilty to felony counts, two for Sullivan and one for Nelson. They will be on three years’ probation, and will either serve six months in county jail or perform 280 hours of cleaning up graffiti and litter.

They will also have to reimburse the city for the cost of cleanup, which could run $8,000 for the Hibernia alone, and cannot have graffiti paint, etching or markers in their possession.

It’s a breakthrough conviction, which not only punishes two of the biggest offenders, but should send a jolt of concern through the tagging community. Marty Ferreira, graffiti abatement officer for the San Francisco Police Department, deserves credit for making the prosecution a personal crusade.

“It’s a frustrating job sometimes,” he said. “What makes it hard is seeing people get away with things. So it was pretty rewarding when this all came together.”

Working with Officer Rob Messier of the Oakland Police Department, Ferreira spent years putting the case together. Sullivan and his “Mike” tag was a particular focus on both sides of the bay.

“He’s been a terror,” Messier said. “San Francisco was trying to get this guy identified and we were, too. He was finally caught at a construction site. He was spraying, he had the paint can in his hand and the paint was wet. Once we got him in custody, things fell into place.”

The San Francisco district attorney’s office, through its Crime Strategies Unit, decided to take the case to a grand jury, rather than a judge. The feeling was that when a tagging case is brought before a San Francisco judge, the charge is often knocked down to a misdemeanor. A grand jury finding would be much more likely to stand as a felony.

The burden of proof was higher, and it was a time-consuming process, but Ferreira was not going to let these cases go.

“I tracked Sullivan’s arrest record in four different states,” he said. “Florida, Massachusetts and New York and here. He was really into posting and showcasing his work on social media.”

Ferreira was able to identify Sullivan’s tag on the Bay Bridge, the Emporio Armani building at Market and Grant and on a Muni Metro car. (A video of the Muni spraying was posted to Instagram.)

“Over the course of a year or so, Rob and I built up a substantial amount of evidence,” Ferreira said. “All of it pointed in the same direction.”

The amount of restitution the taggers will have to pay has not been set yet, but Ferreira says it will almost certainly run to “thousands of dollars.” The Hibernia building cleanup was particularly expensive because sand-blasting the 100-year-old stone is a delicate process. It also requires blocking traffic and using a cherry-picker to get to the work done.

Sullivan will also have to pay for cleanup of the Armani building, the Bay Bridge and that Muni car.

To nail down the case, Messier and Ferreira obtained search warrants for residences, vehicles and cell phone records. Ferreira also testified in the grand jury indictment of Sullivan. He says it was important because Sullivan had done all he could to become a social media icon.

“He was completely dedicated to being a vandal and seems to thrive on the attention,” Ferreira said. “Now he’s got the wrong kind of attention.”

Messier says it was satisfying in Oakland, too.

“A lot of taggers come to Oakland because they know we’re too busy,” he said. “We wanted to send the message: We’re coming after you.”

Not to become over-optimistic, but there’s a hope that cases like this may be a tipping point. Until recently, Ferreira says there was a sense of resignation and inevitability about tagging.

“When I first took this assignment, a lot of people were not even sure graffiti was a crime,” he said. “Now there is no question. People are afraid of paying fines, doing jail time and being put on probation.”

C.W. Nevius is a San Francisco Chronicle columnist. His columns appear Tuesday, Thursday and Saturday. Email: cwnevius@sfchronicle.com Twitter: @cwnevius