Denver Mayor Michael Hancock hammered the final nail in the coffin of a City Council attempt to repeal the city’s long-standing pit bull ban Monday night.

Citing a fear of irresponsible pet owners, should the repeal pass, Hancock vetoed Councilman Chris Herndon’s measure, which council approved earlier this month on a razor-thin margin. The veto was Hancock’s first in three terms.

Herndon expressed disappointment at the mayor’s decision, saying it caught him off guard.

“Not once did the third floor come to me and say, ‘Let’s have a conversation,'” Herndon said.

Ultimately the councilman was unable to rouse the nine votes needed to overcome the veto. He still took the time to list expert organizations that support ending such bans and listed cities across the country that have already repealed their own pit bull bans.

“I’m getting to the point where I’m running out of sources — large and small — to say this is why we should be doing this,” he said.

Herndon’s quest is far from over, though. Now work begins on placing a similar initiative on the November 2020 ballot, he has said.

Council members Amanda Sawyer, Kevin Flynn and others said they could be persuaded to support Herndon’s issue for the ballot with a few tweaks.

For her support, the repeal must pair with increased funding for Denver Animal Protection to ensure compliance and enforcement, Sawyer said.

Flynn said for him, the measure must also require pit bull owners to have liability insurance in case their dog does attack.

Although a public hearing did not accompany Monday’s vote, people for and against Herndon’s measure sat in council chambers. Several spoke during public comment before the meeting began. The vote was received with silence by the crowd, many of whom filed out of the chambers quickly.

Certainly council members were pulled in each direction every step of the way, though the pressure intensified in recent weeks.

Emails, messages and phone calls flooded in to council members opposing the measure. Some offered support, others asked them to reconsider.

Even Gov. Jared Polis waded into the conversation. And Sunday, Hollywood star Justin Theroux weighed in on Instagram, asking Sawyer to reverse her vote.

“I implore you to vote on behalf of the pit bulls that are currently in your shelters and living in the shadows of Denver as a result of Denver’s Ban,” Theroux wrote. “All they want is the right to be available for adoption from your shelter facilities, get registered, microchipped and be LEGAL.”

In his post, Theroux tagged Replace Denver BSL, a local organization meant to end the city’s breed-specific legislation. Co-founder Shira Hereld said since Theroux — who lives in New York City — posted the message, the local organization gained more than 400 new followers.

The added attention could be useful for a push to place a similar repeal on the November ballot.

Denver resident and father Paul Vranas spearheaded much of the public opposition to Herndon’s measure and said he and others would fight the measure fervently if it hit the ballots unchanged.

However, Vranas said he and others could support a ballot measure if it’s changed to also deliver education, higher and reasonable levels of pet registration, promote responsible ownership and compliance with leash laws.