The party atmosphere on the Vegas Strip quickly turned to terror in what has become the deadliest mass shooting in US modern history.
Below are some of the innocent lives lost in the senseless act of violence that authorities are working frantically to piece together - and find a motive.
Sonny Melton, a nurse living in Big Sandy, Tennessee, was attending the concert with his wife, Heather, an orthopaedic surgeon.
The 29-year-old was watching country performer Jason Aldean when the gunman fired into the crowd.
His wife Heather Melton said he saved her life.
"He saved my life. He grabbed me and started running when I felt him get shot in the back," his wife Ms Melton told WSMV News.
"I want everyone to know what a kind-hearted, loving man he was, but at this point, I can barely breathe."
White House spokeswoman Sarah Huckabee Sanders recounted what happened when the gunfire began.
"When the bullets began raining down from above, Sonny shielded her from danger, selflessly giving up his life to save hers," Sanders said.
The couple were married in June 2016.
Quinton Robbins, a 20-year-old university student from Nevada, was reportedly killed at the festival.
His aunt Kilee Wells Sanders took to Facebook to report his death.
"With an incredibly heavy heart. My sweetest nephew has passed away. He was the most kind and loving soul. Everyone who met him, loved him," she wrote.
Jordan McIldoon, of Maple Ridge, British Columbia, died in the arms of a stranger, bartender Heather Gooze, who stayed by his side for hours after promising his mother and girlfriend by cellphone that she would not leave.
"I kept thinking about, 'If this was me would people stay with me? Would they make sure I was OK? Would they contact my family?' I couldn't go," Ms Gooze told ABC News.
The 23-year-old apprentice mechanic was reported dead by his parents.
"We only had one child," Mr McIldoon's parents told CBC News.
"We just don't know what to do."
McIldoon was one of at least three Canadians who died in the shooting.
Denise Burditus, 50, of Martinsburg, West Virginia, attended the concert with her husband Tony, WVVA TV in West Virginia reported.
A smiling Burditus, of Martinsburg, West Virginia, posted a Twitter selfie of herself with her beaming husband, Tony, at the concert just hours before she died.
"It saddens me to say that I lost my wife of 32 years, a mother of two, soon to be grandmother of 5 this evening in the Las Vegas Shooting. Denise passed in my arms. I LOVE YOU BABE," Tony Burditus wrote on Facebook.
Sandy Casey was a special education teacher at Manhattan Beach Middle School in California, KGTV in San Diego said.
Casey was among a group of Manhattan Beach Unified School District staff, the ABC affiliate reported.
“As you can imagine, this loss is impacting many of our staff members deeply,” the superintendent said in a letter sent to district families, KGTV reported.
Angie Gomez was a 2015 alumna of Riverside Polytechnic High School PTSA in Riverside, California, the school said on Facebook.
"She will always be loved and endeared by our Poly Family," the school said.
Gomez was attending nursing classes at a community college after graduating from high school, where she was a member of the cheerleading squad, according to the Los Angeles Times.
She was attending the concert in Las Vegas with her boyfriend.
Charleston Hartfield, 34, was a Las Vegas police officer, a military veteran and the father of two children, according to the Las Vegas Review-Journal.
He was off-duty at the concert and posted a picture from the venue on Facebook shortly before he died. He recently published a book about being a policeman called 'Memoirs of a Public Servant.'
"He was probably busy helping others," Hartfield's friend Troy Rhett told the newspaper.
"I don't know a better man than Charles."
Adrian Murfitt, of Anchorage, Alaska, was a commercial salmon fisherman and was attending the concert with a friend, Brian MacKinnon, who held him as he died, the Alaska Dispatch News reported.
They were taking a picture together when Murfitt was struck by a bullet in the neck, MacKinnon said.
"We just couldn't save him," he said.
John Phippen, of Santa Clarita, California, was a father of five, grandfather of one and owned a remodeling and repair company, KHTS AM 1220 radio station reported.
He attended the concert with his son Travis, who was shot in the arm, the station said.
"If you didn't know John you surely missed out. He had a heart that was larger than life and a personality to match," a GoFundMe page said.
"Even if you were someone he had never met before but were in need, he was there for you."
Travis, an emergency medical technician, took his father to a hospital, where he died.
"He was my best friend," Travis was quoted as saying.
Chris Roybal, of Corona, California, was a US Navy veteran who served in Afghanistan and was in Las Vegas with his mother, Debby Allen, to celebrate his upcoming 29th birthday, according to the New York Daily News.
Roybal's final Facebook post was a response to people who would ask him: "What's it like being shot at?"
His reply. "It's a nightmare no amount of drugs, no amount of therapy and no amount of drunk talks with your war veteran buddies will ever be able to escape."
Dixie Roybal described her husband as haunted by his experiences in Afghanistan, but an adventurous spirit who found joy in life.
"He was always going somewhere, doing something, calling friends," she said.
"He just loved music in general. He was always singing something. He was the best at Karaoke."
One of the many tattoos on his arm celebrated the city of Las Vegas, where he once lived. After the military, he worked at a gym.
Thomas Day Jr.
Thomas Day Jr., 54, of Riverside, California, a home builder, went to the festival with his four children, who are in their 20s and 30s, the Los Angeles Times reported.
"He was the best dad. That's why the kids were with him," his father, Thomas Day Sr., told the newspaper.
Rachael Parker, 33, who was a Manhattan Beach Police Records Technician in California, was shot and died in the hospital.
She and three of her colleagues were offduty and attending the Las Vegas concert when the mass shooting occurred.
A second employee was shot but only suffered minor injuries.
"She was employed with the Manhattan Beach Police Department for 10 years and will be greatly missed," a statement from the department said of Ms Parker.
Hannah Ahlers, a 35-year-old mother of three from Murrieta, California, was shot in the head and died, ABC News reported.
Her children are aged 3, 11 and 14, according to the Las Vegas Review-Journal.
Ahlers was attending the concert with her husband of 16 years, Brian, and three other couples.
Dana Gardner was a 26-year employee of San Bernardino County in California and the mother of three children, according to the San Bernardino Sun.
She was attending the concert with her daughter, who rode with her in an ambulance to the hospital but were not wounded. Fourteen people were killed in San Bernardino in 2015 by a jihadist-inspired couple.
Jennifer Topaz Irvine
Jennifer Topaz Irvine, of San Diego, California, was an attorney with her own practice specialising in criminal and family law, according to The San Diego Union Tribune.
The holder of a black belt in Taekwondo, Irvine was attending the concert with some girlfriends.
A co-worker and friend identified Irvine as a victim to a CBS correspondent.
Jessica Klymchuk, 28, of Valleyview, Alberta, was a librarian and the single mother of four children, Canada’s Globe and Mail reported.
She was a bus driver and librarian at a Catholic school in Valleyview, Alberta. According to her Facebook page, Klymchuk was in Las Vegas with her fiance.
"She's a very good mother. She's raised four beautiful children," Klymchuk’s grandmother Margaret told the paper.
Rhonda LeRocque, of Tewksbury, Massachusetts, was a wife and mother, devout Jehovah's Witness and worked for a Cambridge design firm, the Boston Globe reported.
LeRocque attended the concert with her husband, Jason and their seven-year-old daughter, who were not injured, the newspaper said.
"Rhonda would do everything to be the best mom and the best wife she could be," LeRocque's sister, Jennifer Zelenski, told the paper.
Lisa Romero-Muniz was a secretary at Miyamura High School in Gallup, New Mexico, the Santa Fe New Mexican reported.
In her most recent role, Romero-Muniz offered encouragement and support to students during disciplinary proceedings, the newspaper said.
She was described as outgoing, kind and considerate, it said.
Bailey Schweitzer, 20, was from Bakersfield, California, her brother told the Bakersfield Californian newspaper.
Susan Smith, 53, was a school office manager in Simi Valley, California, the Ventura County Star reported, citing a school district representative.
Smith was an ardent country music fan and worked at an elementary school for three years, the newspaper said.
A school district spokeswoman told the newspaper the mother of three children was a "big country music" fan and she was attending the concert with friends.
Neysa Tonks, of Las Vegas, who worked at Technologent, an Irvine, California-based technology company, was also among the victims, the Los Angeles Times said.
She was the mother of three boys, according to a GoFundMe campaign created by Technologent.
"Neysa brought joy, happiness, fun and laughter to so many of us. The senseless tragedy in Las Vegas Sunday has unnessarily (sic) taken her from our community," the GoFundMe page said.
Carrie Barnette, of Riverside, California, worked at Disneyland for 11 years and was in Las Vegas celebrating a friend's 30th birthday, according to the Los Angeles Times.
"A senseless, horrific, act, and a terrible loss for so many. We mourn a wonderful member of the Disney family: Carrie Barnette. Tragic," tweeted Disney CEO Robert Iger.
Cohen, a Carpinteria resident who died in the shooting. She was attending the festival with her companion Derrick “Bo” Taylor, something they had planned to do together for weeks, KEYT News reports.
One of her two sons, Jeff Rees said: "Our mother was such a strong beautiful and happy woman who made a difference to the lives of everyone she knew.
“She was such a happy person and enjoyed doing the things in life that she loved. We can see by the last photo of her that she was indeed happy and with a person that loves her, Bo."
Derrick “Bo” Taylor
The California correctional lieutenant was attending the concert with Denise Cohen, who was also killed in the attack.
“There are no words to express the feeling of loss and sadness regarding Bo’s passing,” warden Joel Martinez wrote in a memo to staff.
He had worked with the CDCR for 29 years according to KCRA News.
“Our thoughts and prayers are with his family and friends.”