The messages started piling up at 6:38 p.m. on July 11 and kept coming in, past 9:30 p.m.

Don’t let Charles Cohen develop the downtown West Palm Beach tent site, the callers said, 14 of them. "He discriminates against African Americans," they said in identical or almost identical words.

It was an unprecedented campaign against a West Palm developer.

West Palm’s prominent tent site

And in an unprecedented counter, the developer hoping to win rights to build on the city’s prominent downtown tent site is striking back, offering up to $25,000 for information about who was behind the campaign.

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In a statement released Tuesday to The Palm Beach Post, developer Charles S. Cohen, called the July 11 phone campaign "patently false, ugly and unprovoked slander."

"I am offering a cash reward of up to $25,000 to persons who provide valid, relevant and credible information and evidence which materially assists in helping us to confirm and expose the wrongdoers." He established a hotline for people who want to provide information at (561) 650-7125.

The city is about to issue a request for qualifications for the 2.4-acre site, for a developer to design a project that would be "a striking entry feature for the city," according to a draft of the request. The property, at the corner of busy Okeechobee Boulevard and South Dixie Highway, serves as a main visual gateway to downtown and Palm Beach.

Cohen, a part-time Palm Beach resident, and other developers have indicated interest. The city has held off on formally opening the competition, while waiting for city consultants determine how development there should be tuned to ease the flow of people through the increasingly congested downtown. That "mobility study" is scheduled to be completed this summer.

But somebody doesn’t want Cohen in the mix.

The city commission office received at least 14 phone messages last Tuesday evening, all similar, saying Cohen discriminates against African Americans and should not be allowed to develop the site.

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One, for example, identified as West Palm Beach resident Yvonne Beck, left a message saying she opposed Charles Cohen being granted the tent site contract "because he has a history of discriminating against African Americans," according to a paraphrased version of her message that the commission executive assistant distributed to board members.

Caller Danielle Miller likewise "does not feel that a person who does not respect African Americans should be allowed to work in West Palm Beach as West Palm Beach is tolerant of racial diversity," the call summary said.

Cohen, who also has been seeking zoning changes to redevelop the former Carefree Theatre site on South Dixie, declined comment except through the prepared statement distributed through his West Palm Beach attorney, Gregory Young.

"Such malevolence coincided with other attacks on my person and interests," Cohen wrote. "In the past I have been the target of baseless and unsubstantiated allegations. My colleagues and I are engaging with certain authorities to investigate and identify all responsible for promotion of the present, reprehensible actions and false allegations."

The city announced in November it was preparing to put the site back on the market, after previous plans and proposals fell through. Plans for a major digital animation complex fell through when Digital Domain collapsed in 2012. The city commission rejected developer Michael McCloskey’s plans for a major medical complex 2015.

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In March, Cohen submitted an unsolicited proposal to have uber-architect Cesar Pelli design a 300,000-400,000-square-foot office tower for the site, which is walking distance from CityPlace, the convention center, Clematis Street and the waterfront.

The project would give the city "an iconic landmark office tower attracting financial and other service tenants from the surrounding areas and provide the latest technology and amenities found in the very best office towers being built anywhere in the world today," Cohen’s proposal stated.

The New York-based developer owns Cohen Brothers Property Group, which owns 12 million square feet of property in New York, California, Texas and Florida. The portfolio includes a dozen office towers in Manhattan and four design centers in four states, including the Design Center of the Americas, or DCOTA, in Dania Beach.