Coleman could not immediately be reached for comment. Coleman resigned on June 18, before a scheduled interview with investigators, and FEMA officials said they have not been able to question him since.
Online records show Coleman was a senior executive who was paid an annual salary of US$177,150 ($260,000).
In an interview, Long described a "toxic" environment in the human resources department under Coleman at FEMA headquarters.
Starting in 2015, investigators said, Coleman hired many men who were friends and women he met at bars and on online dating sites. He then promoted some of them to roles throughout the agency without going through proper federal hiring channels.
Coleman then transferred some of the women in and out of departments, some to regional offices, so his friends could try to have sexual relationships with them, according to employees' statements during interviews with investigators.
"What we uncovered was a systemic problem going back years," Long said.
He said he has referred several of the cases to the Department of Homeland Security's inspector general, who oversees FEMA, to investigate possible criminal sexual assault.
"The biggest problem I may solve here may be the eradication of this cancer," Long said. "How many complaints were not heard? I've got to make sure we have a safe working environment for our employees."
Long said the problems extend beyond Coleman. The investigation is "not going to stop with him," he said.
Long said he received a direct complaint last year from an employee who said Coleman sexually harassed her. Long forwarded it to the general counsel's office, which started the internal investigation. Coleman was placed on administrative leave in April.
Long is a Trump appointee who has served in his role for 13 months. FEMA officials said the DHS inspector general's office had received complaints about Coleman in 2015 and referred them back to the agency to investigate. It's unclear what became of those complaints under the Obama Administration, the officials said. The inspector general's office did not respond to a request for comment.
Many of the men and women Coleman hired were unqualified yet are still at the agency, officials said. Long said his staff interviewed 73 current and former employees and took sworn statements from 98 people.
Long said many valued employees in the human resources department left because of Coleman's "unacceptable leadership style, good people who wouldn't put up with it."
The preliminary investigation found that an official described as the former chief component human capital officer had sexual encounters with two subordinates, one in 2015 and the other in 2017 continuing into this year. FEMA officials confirmed this person was Coleman.
Both women accompanied him on work trips, but one had few official duties on the trips. When the first woman ended the relationship, Coleman pressured her for dates - then denied her a promotion and tried to fire her, she told FEMA investigators. She said she kept her job by telling him she might be willing to go on dates with him again, according to the preliminary report.
When the second woman said she wanted to leave FEMA, Coleman created a position for her for which she admitted to investigators she was unqualified. He also allowed her to sometimes work from his house, the report said.
Long sent an all-employee email today describing the investigation and steps he is taking to address sexual harassment, including mandatory training by an outside company, new counselling services, a new office to investigate allegations of sexual misconduct and a team of independent contractors to look into pending claims that may have been "inadequately addressed."
He said he went public about the case "to be open and transparent and tell this story rather than people telling it for us."
As sexual harassment has gained prominence in the #MeToo era, federal agencies in the Trump Administration have stepped up training for employees and pledged zero-tolerance policies for perpetrators.
Congressman Elijah Cummings, (D), the top Democrat on the House Committee on Oversight and Government Reform, commended FEMA and called on his committee to hold hearings on the investigation.
Coleman was hired at FEMA in 2011 as deputy personnel chief from the US Secret Service, where he was chief human resources officer for the information technology department.
He was quickly promoted to the top job, overseeing hiring and all personnel policies for the 20,000-person agency and its 10 regional offices.
But Long said the working conditions and morale in his department were "so bad" that Coleman was sidelined to other offices at FEMA on three separate details for months at a time.
"And each time, he was allowed back to his job," Long said.
