Tamara O'Neal was a church-going emergency room doctor who was greatly concerned about gun violence. Dayna Less had survived a neurological disease as a teenager and was planning to get married next year. And Officer Samuel Jimenez had been a Chicago police officer for less than two years and was the loving father of three young children.
On Monday, a gunman shot all three dead in an eruption of violence at Mercy Hospital and Medical Center on the South Side of Chicago.
"It's a senseless loss of life," Patrick Connor, director of emergency medicine and chair of the emergency department at the hospital, said at a news conference Tuesday afternoon.
He described all three victims as "young vibrant people with very bright careers."
Dr. O'Neal, 38, led her choir at church every Sunday, Connor said.
"She had one request when I became director of the emergency department," Connor said. "We struck a bargain that she would not have to work on Sundays because she was such a big part of her church, where she was in charge of the choir."
She'd only worked at Mercy Hospital for about two years before she was gunned down Monday by a man she had broken up with who confronted her to demand she give back an engagement ring, police said Tuesday.
Police identified the gunman as Juan Lopez, 32, who died in the rampage, authorities said. An autopsy by the Cook County Medical Examiner's Office showed that Lopez died from a self-inflicted gunshot wound to the head.
O'Neal's father, Thomas O'Neal, recalled the last conversation he had with his daughter over the weekend.
"She said 'I love you.' That's the last words she spoke to me," Thomas O'Neal told ABC Chicago station WLS-TV.
As an ER doctor, O'Neal often expressed concern about the toll of gun violence she saw on a regular basis.
"She talked about it a lot, and about the incessant national tragedy that all these people were dying needlessly," Connor said.
Conner added that O'Neal was shot to death at the end of her shift on Monday.
"She had no children. Never missed work. The best person ever, really," Connor said.
During a news conference Tuesday afternoon, Stephanie Loudin, the nurse manager at the hospital, said O'Neal started as a resident at Mercy after graduating from the University of Illinois at Chicago and became part of the medical staff in 2016.
"She was well liked, well respected and we will miss her," Loudin said.
Connor added that when he took over the emergency department in 2017, O'Neal was of great help to him.
"Without her, we couldn't have done it," Connor said, describing O'Neal as a "fantastic" person."
"If I was in extremis and about to die, I would love for Dr. O'Neal to be near to take care of me," Connor said.
Dayna Less, 25, graduated from Purdue University in May and was a pharmacy resident in training at Mercy, having joined the hospital in July. She was inside a hospital elevator when a bullet fatally struck her, police said.
"I do not want Dayna remembered as a victim, and I want everyone to understand that," her father, Brian Less, said in an emotional news conference Tuesday. "Dayna was a very special person. She had unique gifts. She was intelligent, she was funny, she was kind. She was a good friend and has good friends."
He said his daughter was planning to get married to her fiancé, Adam Keric, next June.
"It was a match made in heaven. We were planning a wedding of over 500 people, and I was going to be giving a wedding speech instead of a eulogy," Brian Less said.
He said that at the age of 15, his daughter suffered a neurological disease that required her to undergo a series of surgeries at Georgetown University in 2011.
"They brought her back to us," he said. "Dayna decided at 16 years old that she had been given her chance at life back and she was going to freely give her life to everyone she could. She was going to give of herself."
He said his daughter and his wife, Teena, started the blog MyDaughtersHeadache.com to help children who suffer from afflictions like the one she endured as a teenager.
"She realized then that she could not sit still and only wanted to help others and the less fortunate," her father said, adding that his daughter spent time in Keyna helping at a hospital.
"She was forged in her own adversity which made her the strongest person I will ever know," he said.
Officer Samuel Jimenez
Officer Jimenez, 28, died from gunshot wounds suffered when he arrived on scene and chased the alleged gunman, Juan Lopez, 32, into the hospital.
Jimenez was shot to death in the lobby of the hospital during a gunfight with the suspect, police officials said.
"We cannot thank him enough for his courage and bravery," Connor said of Jimenez. "A hospital should be a safe place. Every shooting in America is a tragedy -- it is a national tragedy. And it is especially senseless when a shooting occurs in a healing space of a hospital."
Jimenez, 28, a married father of three young children, "saved a lot of lives," said Chicago Police Superintendent Eddie Johnson, adding that police vigorously pursued the suspect because they "just don't know how much damage he was prepared to do."
Chicago Mayor Rahm Emanuel praised Jimenez and his colleagues who responded to the shooting, saying Tuesday that they "did save and potentially prevent a lot worse loss of life,"
"Today, the Fraternal Order of Police lost a valued brother -- a courageous police officer who got up this morning, went to work and wanted to protect the city of Chicago," said Kevin Graham, president of Chicago chapter of the police union. "He did that today, and he did so with his life."
ABC News' Joshua Hoyos contributed to this report.