Boxing promoter Bob Arum was devastated by the death of Patrick Day from a brain injury after his most recent fight. (1:31)

Junior middleweight Patrick Day, who suffered a 10th-round knockout loss Saturday night, died from brain injuries Wednesday at Northwestern Memorial Hospital in Chicago, promoter Lou DiBella said. Day was 27.

"On behalf of Patrick's family, team, and those closest to him, we are grateful for the prayers, expressions of support and outpouring of love for Pat that have been so obvious since his injury," DiBella said in a statement. "He was a son, brother, and good friend to many. Pat's kindness, positivity, and generosity of spirit made a lasting impression with everyone he met."

Day was knocked down by right hands in the fourth and eighth rounds by unbeaten Charles Conwell, a 2016 U.S. Olympian, during the scheduled 10-round fight on the Oleksandr Usyk-Chazz Witherspoon undercard at Wintrust Arena.

Although Conwell was clearly winning the fight, Day was competitive in many of the rounds. However, in the 10th round, Conwell landed two rights and a left hook that knocked out Day. When Day went down, the back of his head slammed onto the canvas, and referee Celestino Ruiz immediately stopped the bout without a count at 1 minute, 46 seconds.

Patrick Day, 27, died Wednesday, four days after suffering brain injuries when he was knocked out in the 10th round by Charles Conwell. Al Bello/Getty Images

Day was immediately surrounded by medical personnel and within minutes was taken out of the ring on a stretcher and to an ambulance.

He never regained consciousness. At one point he had a seizure and then lapsed into a coma before undergoing emergency brain surgery.

Members of Day's family flew to Chicago on Sunday morning to join manager/trainer Joe Higgins and Alex Dombroff, who works for DiBella, in keeping vigil, but the situation was dire and doctors gave Day little chance for survival.

On Wednesday, surrounded by his parents, other family members, Higgins and close friends, Day was disconnected from the machines that had been keeping him alive.

The bout was streamed live on DAZN, which offered its condolences on Day's death.

"DAZN is incredibly saddened to learn about the passing of Patrick Day," a company spokesman said in a statement. "Our heartfelt thoughts are with his family and friends during this difficult time."

Two days before Day's death, Conwell, struggling with what had happened, posted an emotional letter to Day on social media.

Kriegel on Patrick Day ESPN's Mark Kriegel looks at the life of Patrick Day and the retired firefighter and 9/11 first responder who trained him. Read here

"I never meant for this to happen to you," Conwell wrote. "All I ever wanted to do was win. If I could take it all back I would. No one deserves for this to happen to them. I replay the fight over and over in my head thinking what if this never happened and why did it happen to you. I can't stop thinking about it myself. I prayed for you so many times and shedded so many tears because I couldn't even imagine how my family and friends would feel. I see you everywhere I go and all I hear is wonderful things about you."

Day (17-4-1, 6 KOs), of Freeport, New York, came into the fight having lost a 10-round decision to emerging junior middleweight contender Carlos Adames on June 28, but he posed by far the stiffest test so far in Conwell's career.

"During his short life, boxing allowed Patrick to impact many communities, both big and small," DiBella said in his statement. "In his hometown of Freeport, Long Island, he was a beacon of light and the star pupil at the Freeport PAL, the gym he trained in from the moment he began boxing until the last bout of his career. He was recognized as one of Long Island's finest professional fighters for years. He was a fixture in the boxing community throughout New York City. Patrick was even known in Japan, which he visited to spar with his friend and colleague, world champion Ryota Murata."

Before the back-to-back losses, Day had won six fights in a row dating to 2015 and was a standout amateur.

"Before establishing himself as a world-class professional fighter, Pat was a highly decorated amateur," DiBella said. "He won two nationals titles, the New York Golden Gloves tournament and was an Olympic team alternate, all in 2012. Day turned pro in 2013 and overcame early career struggles to become a world-rated [junior middleweight] contender. He captured the WBC Continental Americas championship in 2017 and the IBF Intercontinental championship in 2019. In June 2019, he was rated in the top 10 by both the WBC and IBF.

"He was also a dedicated college student, having earned an associate's degree in food and nutrition from Nassau Community College and, subsequently, a bachelor's degree in health and wellness from Kaplan University."

Unlike many who turn to boxing as a means to escape poverty, Day came from a middle-class family.

"Patrick Day didn't need to box," DiBella said. "He came from a good family, he was smart, educated, had good values and had other avenues available to him to earn a living. He chose to box, knowing the inherent risks that every fighter faces when he or she walks into a boxing ring. Boxing is what Pat loved to do. It's how he inspired people and it was something that made him feel alive."

DiBella said he hopes Day's death will lead to finding a way to make boxing a safer sport.

"It becomes very difficult to explain away or justify the dangers of boxing at a time like this," DiBella said. "This is not a time where edicts or pronouncements are appropriate, or the answers are readily available. It is, however, a time for a call to action. While we don't have the answers, we certainly know many of the questions, have the means to answer them, and have the opportunity to respond responsibly and accordingly and make boxing safer for all who participate.

"This is a way we can honor the legacy of Pat Day. Many people live much longer than Patrick's 27 years, wondering if they made a difference or positively affected their world. This was not the case for Patrick Day when he left us. Rest in peace and power, Pat, with the angels."