(CNN) Dr. Lorna Breen was not struggling with any emotional difficulties or problems with stress prior to being on the front lines of battling a pandemic, her father says.

The New York City emergency room doctor who recovered from Covid-19 and continued to treat coronavirus patients died a hero, he says.

The 49-year-old's father, Dr. Philip Breen, spoke to CNN's Chris Cuomo Tuesday.

"She was a doctor, every bit of the word that a doctor should be," Breen said. "She put her life on the line to take care of other people. She was in the trenches, so to speak, right in the front line as people were dying left and right around her."

Breen said his daughter contracted the virus and stayed home for just over a week, which in hindsight, he feels wasn't enough time.

"I think she felt an overwhelming sense of wanting to help her colleagues and her friends who were still fighting the good fight, and so she strapped on her harness and took the bit in her mouth and she went back," Breen said. "I talked to her just before her final 12-hour shift. And during the time she was on that shift, she basically went down in the traces like a horse that had pulled too heavy a load and couldn't go a step further and just went down."

Breen said his daughter was hospitalized until she was determined to be well enough to be out on her own, but she was "clearly not better."

"As of Sunday, she took her own life because I think she was tired and she was the kind of person, as somebody has very aptly put it, she was like the fireman who runs into the burning building to save another life and doesn't regard anything about herself. So she has paid the price and she's been in the trenches," Breen said.

She was hospitalized and treated for exhaustion

Lorna Breen was admitted to the hospital at the University of Virginia for exhaustion, her father said, adding that her mother is a doctor in the ward where she was treated.

After about a week, she left the hospital to stay with her mom, her father said. Then, last weekend, she went to stay with her sister, and that is where she died.

Officers responded Sunday to a call for medical assistance and identified the victim as Breen, the Charlottesville Police Department said in a news release. She was taken to University of Virginia Hospital for treatment and "later succumbed to self-inflicted injuries," police said.

"Frontline healthcare professionals and first responders are not immune to the mental or physical effects of the current pandemic," said Charlottesville Police Chief RaShall Brackney. "On a daily basis, these professionals operate under the most stressful of circumstances, and the coronavirus has introduced additional stressors."

"Words cannot convey the sense of loss we feel today," the New York City hospitals where Breen worked said in a statement.

"Dr. Breen is a hero who brought the highest ideals of medicine to the challenging front lines of the emergency department," they said. "Our focus today is to provide support to her family, friends, and colleagues as they cope with this news during what is already an extraordinarily difficult time."

How to get help: In the US, call the National Suicide Prevention Lifeline at 1-800-273-8255. The International Association for Suicide Prevention and Befrienders Worldwide also can provide contact information for crisis centers around the world.