After additional interviews with witnesses, police also offered a somewhat changed description of the suspects. Initially, the men were described as being of either Middle Eastern or Indian descent. Tuesday, police said the suspects may be Hispanic.
One suspect was described as being about 20 years old, 5-foot-10, thin, and wearing a white shirt with blue stripes. Another suspect was described as being about 20, 6-feet tall, and wearing a maroon shirt. Little was known about the other two men.
It was just before 2:30 a.m. when Kless, his girlfriend, and another female friend tried catching a cab near Fourth and Chestnut Streets, police said.
The three friends had just left Lucy's Hat Shop Restaurant & Lounge a few blocks away. The street was clogged with taxis.
Kless flagged a cab whose lights were on, signaling it was free, and began talking with the driver, investigators said Tuesday.
The driver either already had people in the cab or did not want to travel the short distance Kless had requested, investigators said.
Kless then yelled something along the lines of "Turn off your f---ing light!" At the same time, police said, the four suspects pulled up a few cars down and called out to Kless' companions.
Two of the men in the car apparently thought Kless was yelling at them, jumped out, and rushed Kless without warning, investigators said. A third man from the car quickly joined the attack.
One of the assailants smashed Kless' head against a low stone wall near the Second Bank of the United States building, an investigator said. Kless never regained consciousness and died 17 hours later at Thomas Jefferson University Hospital.
Police have recovered grainy footage of the car, believed to be an older model reddish or maroon four-door sedan, possibly a Mazda.
Detectives searched buildings from Front to Broad Street, between South and Market Streets, trying to track the path of the car and hoping for a clear image of it, investigators said. The three-day holiday weekend had slowed the search, since many buildings in the historic district were closed Monday.
Investigators continued to canvass Old City bars for patrons or employees who might have seen the attack.
Police reiterated their calls for the driver of the vehicle, who did not participate in the attack, to turn himself in to authorities. Police Commissioner Charles H. Ramsey has said that the District Attorney's Office might look more favorably on the driver if he worked with investigators.
"Right now, the best thing for the driver to do is to get himself to us before we come and find him," said Lt. Ray Evers, a police spokesman.
In his hometown of Warwick, N.Y., Kless' family and friends prepared for a weekend funeral service.
Kless, who graduated from Temple in 2010, had recently returned to Philadelphia after landing a job in the Philadelphia office of Marsh, a major insurance-brokering and risk-management company.
His friends have opened a Facebook page called "Justice for Kevin Kless," asking any witnesses to step forward.
Police said additional reward money from private donors was expected to be announced in the next few days.
Contact staff writer Mike Newall at 215-854-2759, firstname.lastname@example.org, or @MikeNewall on Twitter.