Boston Mayor Michelle Wu quietly left town for a family vacation this week without informing the city council president, leaving him unaware that he was the acting mayor for several days.

A Wu spokesperson said the mayor was “squeezing in some family time this last week before school starts,” but did not provide the dates for when she left town and would be returning to Boston.

“She is available and checking in with the team as usual,” her spokesperson told the Herald on Tuesday.

A City Hall source said Wu hasn’t been seen in Boston since she joined Police Commissioner Michael Cox Saturday to provide an update on an early morning shooting in Dorchester that left eight people injured.

While Wu’s office wouldn’t say what date she left town, the mayor was absent from two press conferences on Monday and Tuesday, where Cox provided an update on juvenile violence and her administration announced a policy change she had pushed for as a city councilor.

Her public schedule was also blank, aside from a virtual community meeting she attended on Monday evening, for the first three days of this week.

While the city charter dictates that the council president assumes the role of acting mayor during a mayor’s absence from the city, a source told the Herald Ed Flynn had not been notified until Tuesday afternoon that Wu was out of town.

This effectively left the city without an acting mayor, or at least one who was unaware that he was in charge, possibly for several days.

Wu had sought to leave town quietly, given the public attention her 10-day vacation received earlier this month, the source said, adding that she may have also been unhappy with how active Flynn was when he was acting mayor during that time.

The mayor’s last vacation began on Aug. 3, a day after she announced her administration planned to take a “major step” to address the escalating violence in the Mass and Cass zone. The plan was not laid out until last Friday, however, or several weeks later.

While Wu was away, Flynn joined Boston Police officers for a tour of Methadone Mile, a move that also attracted quite a bit of media attention.

Flynn told the Herald Tuesday that he was notified he was acting mayor, but wouldn’t say when the notification was made.

“I talked several times to Mayor Wu over the last few days about public safety issues, Mass and Cass and other citywide issues,” Flynn said. “I talked with Police Commissioner Cox about the violent attack on two police officers. Tomorrow’s City Council meeting includes an important discussion of Mass and Cass as the proposed ordinance will be introduced and assigned to committee.”

“I share the administration’s urgency to give the Boston Police the clarity and authority they need to take appropriate actions,” he added, referring to Wu’s proposed ban on tents and tarps at Mass and Cass. “It’s critical we work together, support our police and their families, and address public safety concerns.”

Larry DiCara, a former city councilor and longtime observer of Boston politics, said that while he was notified when he had to step in as acting mayor during his time as council president in the 1970s, such notice is not as “essential” with today’s technology.

“The charter was written over 100 years ago when the world was a very different place,” DiCara said. “I would argue that if you’re easily reachable, like you’re on the beach or on the Cape, that probably it’s not essential. But if you’re out of state, probably the spirit of the charter would be that you notify.”

In the current world, he said, Flynn likely has Wu’s cell number, “and if something really happens, he can find her, so I wouldn’t be overly alarmed about it.”

DiCara cited the juvenile violence that occurred this weekend outside AMC movie theaters in South Bay and Downtown Crossing, stating that police handled the situation well. If the problem spun out of control, however, Wu could have directed Flynn to make a “tough decision” in his capacity as acting mayor, he said.

“For example, it would have been declaring a state of emergency and keeping people indoors,” DiCara said. “That’s a decision only the mayor could make, and if Michelle was out of town, he would have to make it.”

While Wu has taken two lengthy vacations this month, he said it doesn’t necessarily strike him as a lot of time off.

“The average American takes vacation,” DiCara said. “And I’m guessing most weeks she puts in 70 to 80 hours so she deserves it.”