The families of 120 elderly residents of a soon-to-close Brooklyn assisted living facility will take their cause to the streets this week, and maybe to the courts.

Prospect Park Residence, a 15-year-old, nine-story building in the Park Slope neighborhood across from Grand Army Plaza, announced at an emergency meeting two weeks ago that it will “surrender its operating license” to the state Department of Health — in other words, go out of business — within 90 days.

“The families were stunned — people were very, very upset,” said Emily Berger, whose 89-year-old mother, Mary, has lived in the Residence for five years.

The residents’ relatives, mostly children, immediately started looking for new housing in the Greater New York area for their fathers and mothers, Berger told The Jewish Week.

And, at a crowded public meeting Monday night at nearby Congregation Beth Elohim, many of the relatives — who are communicating with each other in a private Google group — decided to sponsor a rally on Saturday at 10 a.m. at the farmer’s market near the Residence. And they are “investigating legal options” to block the building’s closing, Berger said. “The plan is to stop it, if possible.”

“It’s a grassroots thing.” The relatives “want to make sure their voices are heard,” she said. “We want to let people know” the plight of the soon-to-be-displaced seniors, and of the 67 staff members who will lose their jobs.

The Residence offers kosher food in its dining area and weekly visits by a rabbi, Berger said, and the facility, which admits residents on a nonsectarian basis, has a majority-Jewish population.

“Since 2009, Prospect Park Residence’s ownership and management have taken extraordinary steps to ensure a stable and predictable environment for its residents and staff by absorbing escalating costs,” the facility’s executive director, David Pomerantz, said in a statement. “However, five years later, the economic recovery remains sluggish and the company’s tax obligation has sky-rocketed — increasing by nearly $1 million. Today, despite its best efforts, Prospect Park Residence is no longer viable.”

Pomerantz said the Residence initiated a “process of an appropriate transition to new accommodations” for the residents, some of whom live in a dementia unit.

“Since the announcement, management has been making one-on-one appointments with the residents and their families to help evaluate individual needs and preferences, and examine the available resources in the community,” a spokesman for the Residence told The Jewish Week in an email message. “Residents will not be left without a place to go. The intent is to safely and seamlessly relocate residents to other residences that will meet their needs.”

The spokesman for the building said “there are no immediate plans for the building.”

Rabbi Andy Bachman, spiritual leader of Beth Elohim, called the residence’s closing “plainly immoral” in a written statement given to the local blog, F–ked in Park Slope.

The decision “lacks basic Jewish values of decency,” the statement adds, alluding to the owner, Haysha Deitsch, reportedly a member of the chasidic group Chabad-Lubavitch.

The rabbi told the news website DNAinfo.com that he and several members of his congregation have had relatives living in the Residence; he said Beth Elohim members may take unspecified steps to keep the facility from closing.

Berger said her mother, a Bronx native who had lived out-of-town for several decades, moved back to New York in 1982, worked as a fundraiser for UJA-Federation of New York, lived on the Upper West Side, and moved to the Brooklyn residence because of “health difficulties.”

Berger lives two blocks from the Residence; another sister lives in the area. “I see her at least once a week, often more often,” she said. Grandchildren stop by frequently to visit in the Residence. “She has been happy there,” she added.

The residents “have a community” in the building, with many age-appropriate activities, Berger said. She called the closing of the Residence “like breaking up a village. It’s very hard for the elderly. Some … are very fragile and can’t handle the uncertainty. It’s total uncertainty at the end of their lives. They felt they had a place where they could age in place.”

For information, contact Emily Berger at eberger90@aol.com.