The old Italians came with picket signs because they were ticked off about the closing of a North End nursing home. Young professionals hoisted their own placards to protest a proposed hotel on Lewis Wharf. Another picket sign addressed the height of the controversial Harbor Garage project.

And the swarm of television cameras and reporters? They wanted Mayor Martin J. Walsh to comment on the indictment of a second city department head in a growing federal corruption investigation that has dogged his administration.

The event was supposed to be an idyllic neighborhood coffee hour at Christopher Columbus Park, where local volunteers hoped to highlight the bumper crop of roses. But these days, there are few peaceful events for Boston’s mayor.

Walsh tried unsuccessfully to mingle with the crowd because he was swarmed by cameras and protesters. The hubbub left the mayor no choice: He marched away from the coffee hour and held an impromptu press conference, urging the media to give him space at the event. Then the mayor took three minutes of questions from reporters.

Walsh expressed concern about the indictment; said he felt bad for his aide, Timothy Sullivan; and made clear that “if these allegations are true, I’m not happy.’’ Walsh again declined to answer questions about whether he had appeared before a grand jury and had a touch of exasperation in his voice when a reporter asked whether the indictment marked the end of the federal investigation.

“Certainly, I hope so,’’ Walsh said. “I read the indictment today, and it didn’t seem like there was anything else that was going to come.’’

After the press conference, Walsh tried to return to the coffee hour, but he was thwarted by the nursing home protesters, who peppered him with questions. The 140-bed Spaulding Nursing and Therapy Center North End is slated to close because Partners Healthcare announced it was moving the operations to a facility in Brighton. Protesters held picket signs reading, “Save our North End Nursing Home.’’

“We don’t want the place to be closed, and we don’t want the residents to go to another facility,’’ said Michael Graffo, a 75-year-old from New Bedford who said his 99-year-old mother lives in the North End Spaulding facility. “This is their home. If you move these people out of their home, you’re going to kill these seniors.’’

The coffee hour buzzed with volunteers from Christopher Columbus Park and top city officials, who exchanged grim looks. Finally, the mayor stepped up to speak to the crowd and address the protesters, talking first about the proposed hotel and his love of the waterfront and second about the nursing home.

In both cases, Walsh said it was early in the process, and he recognized the passion surrounding the issues. His administration, Walsh said, would be engaged with the community and other elected officials.

“I want to thank you for [your] advocacy,’’ Walsh said. “In saying all that, I want to thank everybody for coming out today. Also, there’s probably other things that you are concerned about.’’

Walsh then deployed self-deprecating humor, which can be one of his most charming attributes. The mayor recognized state Representative Aaron Michlewitz, who was in the crowd. “I’m going to ask Aaron to come on up and say a few words,’’ Walsh said. “He might not want to, but please come up.’’

Laughter rippled through the crowd. Then, City Councilor Salvatore LaMattina stepped up to speak.

“Let’s hear it for the mayor,’’ LaMattina said. The crowd broke into applause. Walsh smiled.

Andrew Ryan can be reached at acryan@globe.com Follow him on Twitter @globeandrewryan.