The call gave investigators the break they needed, said Lt. Mark Deegan, of SIU, which handled the case. Hoping to collect a $20,000 reward, the tipster went to police headquarters Thursday, and more details quickly emerged.
Ferguson and two friends, identified by police as Felix Carrillo, 23, and Kenneth Santiago, 19, had met Jan. 13 at the hotel in Society Hill where Ferguson worked, for a night on the town, the tipster said.
They spent the evening bouncing around Center City bars and clubs in Ferguson's green Toyota. When they returned to the hotel in the early morning, another witness overheard them laughing and bragging about the beating, investigators said.
By Friday afternoon, U.S. marshals and investigators from the homicide fugitive unit had taken Ferguson from his Fox Chase home to police headquarters for questioning.
By late Friday, Carrillo, of Olney, and Santiago, of Juniata Park, who told police they were cousins, were also in custody, charged with murder.
None of the suspects had a criminal history, Homicide Capt. James Clark said.
No one answered the door at either Santiago's or Carrillo's home Saturday. A woman who answered the door at Ferguson's home declined to comment and shut the door.
Ferguson worked at the Sheraton for Towne Park, a hospitality business that contracts valets to the hotel, a Towne Park spokesman said, declining other comment. Sheraton representatives referred questions to Towne Park.
One valet, who did not want his name published, described Ferguson as a "nice kid who got along with everybody."
Ferguson had taken courses at the Pennsylvania State University's Abington campus and had recently talked about joining the military, the coworker said.
According to police, the suspects' statements confirmed the sad narrative that had emerged about Kless' death in news reports.
Ferguson and the other suspects were driving back to the Sheraton to pick up another car when they came across Kless, his girlfriend, and another woman, who had just left Lucy's Hat Shop Restaurant & Lounge, police say.
Someone in Ferguson's car yelled something to the women, investigators said.
At the same time, Kless was having a brief exchange with a cabdriver who had stopped but refused to take them the short distance Kless requested.
Kless cursed as the cabdriver drove away, and the suspects may have thought he was shouting at them, investigators said.
It is not known what words, if any, Kless exchanged with his assailants, who rushed from the car and began punching Kless in front of the historic Second Bank of the United States building, police allege.
During the assault, Kless' head struck a low stone wall.
Until the tipster called, the investigation had proved frustrating, Deegan sad.
Investigators had only grainy security-camera images of what they could only make out as a four-door sedan. Initial witness reports, which proved inaccurate, suggested the car was a red or maroon Mazda.
There were other challenges.
Security cameras in the tower of Independence Hall, which might have captured the attack, were not operating because of a renovation project.
The National Park Service helped police by reviewing hundreds of hours of video from other security cameras, Deegan said. Police reviewed scores of videos from local merchants' security cameras, but were hampered by their lack of information about a car type or suspects' descriptions.
Investigators tracked down other cabdrivers who were in the area, but they remembered seeing only glimpses of a fight, Deegan said.
A group of men in a Cadillac, whom Kless' girlfriend and other companion ran to for help, but who pulled away, could not be located.
In the end, the $20,000 reward offered by the city and police proved critical.
Kless, who had recently landed a job at the Philadelphia office of Marsh Insurance, was buried Saturday in his hometown of Warwick, N.Y.
In the days after the attack, Kless' family had pleaded with someone to come forward with information.
On Saturday, after burying her son, Kendall Kless said in a statement: "While we are elated to hear of the apprehension of the men who brutally beat our son to death, it is no consolation for the pain and suffering they inflicted on Kevin, our family and friends."
She thanked the Philadelphia police for capturing the three suspects, and she said, "We look forward to seeing them pay for their crime."
Contact staff writer Mike Newall at 215-854-2759, firstname.lastname@example.org, or @MikeNewall on Twitter.
Staff writer Suzette Parmley contributed to this article.