ORLANDO, Fla. (AP) — Leaders of a private foundation working to build a museum and memorial to honor the victims of a massacre at a gay nightclub in Florida said Friday that they were dropping their plans to build a museum, even as the city of Orlando is moving ahead with constructing the memorial.

Officials with the onePulse Foundation said in a public letter that they are unable to move ahead with a museum to commemorate the 49 people who were killed and 53 victims injured when an attacker opened fire in the gay nightclub in June 2016. A SWAT team killed the shooter, who had pledged allegiance to the Islamic State group, following a standoff.

At the time, it was the worst mass shooting in modern U.S. history. But that number was surpassed the following year when 58 people were killed and more than 850 were injured among a crowd of 22,000 at a country music festival in Las Vegas.

Fundraising and planning for the project slowed down during the COVID-19 pandemic and once shutdowns eased up soaring construction costs made the project “financially unrealistic to complete as originally conceived,” the letter said. The onePulse Foundation had said earlier this year that it was scaling back from its plans after determining that the price of the project could reach as much as $100 million.

Orlando city council members earlier this week approved purchasing the Pulse property for $2 million with the intention of building the long-awaited permanent memorial for the victims.

The efforts to build a memorial and museum for Pulse victims has been moving slowly since the massacre. Until this month, the nightclub’s owners hadn’t agreed to sell the property, and the plans to build a museum had been slated for a nearby site that was purchased for $3.5 million by the onePulse Foundation using funds raised from Orange County’s tourism tax.

The foundation has spent another $3 million of Orange County tourism tax dollars on a design for the project. Orange County said in a news release Friday that the parcel will be returned to the county since a museum isn’t going to be built there.

One of the nightclub’s owners, Barbara Poma, had been executive director of the onePulse Foundation but stepped down last year and left the organization entirely earlier this year.