They were stunned and grief-stricken over his murder in Old City.
"He has changed every person's life who has ever been around him," Maria Hergan said.
"We just all feel robbed of a great person," Sean Brondi said.
Kevin was killed early Saturday morning.
He and two female friends had just left Lucy's Hat Shop Restaurant and Lounge around 2:30 a.m.
Investigators say Kevin Kless was trying to hail a cab in front of the Historic Second Bank of the United States on the 400 block of Chestnut Street.
Police say the cab did not stop and Kless yelled at the driver, and three men in a maroon car who apparently thought he was yelling at them got out and slammed his head into the wall and sidewalk.
As U.S. Park Rangers were running to help, they saw the suspects, possibly of Middle Eastern descent, taking off in a 2000-2003 maroon 626, 4-door Mazda, similar to this one.
The Temple University graduate died hours later at a local hospital.
Kless' friend Owen McDaniel said it was just a senseless act of violence.
"No reason for it and it's absolutely ridiculous and they need to be found. They need to be tried and they need to rot in jail for the rest of their lives," McDaniel said.
"The most uniquely funny person that I've ever met; he gave us so much joy and laughter," said friend Beth Umstette.
"Every time you were with him, it was always a memory. We are all just a family; we're such a tight knit group," friend Frank Samsel said.
All of these friends Action News interviewed say they rushed to the hospital after learning of Kevin's grave injuries.
His parents and two older brothers soon arrived from Warwick, New York, where Kless grew up. They soon learned Kevin was dead.
Action News spoke to the victim's mother, Kendall Kless, over the phone Sunday night.
"There is no explanation for it. No way to excuse it. No way to understand it or explain it. We are devastated at this loss," Kendall said.
Kevin's mother urged witnesses to say what they saw.
"We plead for people to come forward. People walked by the fight and witnessed it. We are urging people to come forward and call police as soon as possible," Kendall said.
Kendall says her son was an organ donor and three of his organs have been donated.
"We helped three people," Kevin's mother wrote in an e-mail to Action News.
Kendall also sent in a photo of Kevin from a recent Halloween party where he dressed as an 'Indian in a Cupboard' based on the children's book and film.
"That's just a taste of his personality. You'd have to know him to appreciate what a fun, funny, great kid he was," she wrote.
Anyone with information about the attack or the suspects' car is asked to call Philadelphia Police.
(Note: Photo courtesy of Gamma Iota Sigma - Sigma Chapter Temple University)
The Associated Press contributed to this report.