A 36-year-old man died yesterday afternoon within an hour of being beaten by four youths on a SEPTA platform a short distance from City Hall and the Center City Starbucks store where he worked. The attack happened in view of passersby and a transit policeman who was unable to help.

Police said last night they had charged one of the teenagers, a 16-year-old student at Simon Gratz High School, with murder and conspiracy in the beating death of Sean Patrick Conroy, who lived in South Philadelphia and managed the Starbucks at the Philadelphia Marriott Downtown, 12th and Market Streets.

The three other youths involved in the attack were being sought last night.

The four went after Conroy at 2:35 p.m., authorities said. He had just gotten off work and was on the platform of the westbound Market-Frankford El below 13th and Market Streets. A steady stream of commuters was coming and going.

SEPTA Police Capt. Steven Harold said a sergeant who routinely patrols the 13th Street concourse was on the eastbound side when he saw the victim in some sort of dispute with four juveniles.

"He was in a defensive posture," Harold said of Conroy. "Apparently, these males were doing something he wasn't prepared for. This was not a friendly conversation."

The sergeant saw one of the youths take a swing at Conroy, Harold said. The sergeant rushed to the other side of the platform, but by the time he arrived, the youths had fled.

Other people were on the platform, Harold said, but left when the sergeant approached.

Conroy went "into some type of difficult breathing, chest pains, palpitations," Harold said. "He was in obvious distress."

"No one tried to help," Harold said. "It just looked like a disturbance."

The sergeant administered cardiopulmonary resuscitation until emergency crews arrived. The victim was pronounced dead at Thomas Jefferson University Hospital at 3:09 p.m.

Officials found no blood at the scene, and the victim had no visible lacerations or bruises, Harold said.

Though Conroy was not able to give the sergeant any details about the fight, police said, the officer was able to identify one of the youths, the 16-year-old who was charged last night. His name was not released.

Police Lt. Mel Williams said the teen had no police record.

The boy is a student at Gratz, Philadelphia School District officials confirmed. The school, in North Philadelphia, dismisses its students at 3:04 p.m.

Police last night said that they did not have a motive for the assault, but that it did not appear to have been a robbery. The cause of death also was unclear, and an autopsy was scheduled for today.

An employee at another Starbucks store in Center City described Conroy as a hardworking "nice guy" who managed the store at 12th and Market.

He always wore a Starbucks baseball cap, said Winter Pace, 42.

"That happened in broad daylight. I have to leave here at night and catch a bus right where it happened, and that makes me very nervous," Pace said.

Inside the Starbucks where Conroy worked, solemn-faced employees made lattes, rang up customers, and said they could not speak about their colleague. They referred reporters to corporate headquarters in Seattle, which last night released a statement.

"We have been informed by the Philadelphia Police Department that a Starbucks store manager has passed away as a result of an incident that took place earlier in the day," the statement read.

"Our deepest sympathy goes to the family and friends of the partner, a longtime and well-respected Starbucks employee. Out of respect for the partner's family, we will refrain from sharing additional details at this time."

Conroy's Starbucks closed early out of respect for his death, a sign posted outside said.

The attack, near the Convention Center and a short walk from the historic area, shook the security of commuters who consider central Philadelphia safe.

With heavy pedestrian traffic above, the 13th and Market platform is not considered a trouble spot.

"We have no problems here, usually," Harold said. "It's not what you'd call a really crowded platform, but it's always steady."

"Beaten in broad daylight?" said Richard Wilkinson, 48, a cook who works in Center City and lives in Southwest Philadelphia. "It's usually pretty safe here, but things are getting out of hand."

Wilkinson said he was worried. "It's just the beginning of spring, and how bad is it going to get as we get to summer," he asked, "when things get warmer and more people are outside?"

The death hit Derrick Anderson hard. At 38, he is just two years older than the victim, and like him, he regularly uses the El.

"There's so many people around," Anderson said. "You'd think that was no time for trouble. What is going on with this world?"

Carl Larson, 44, in town from Minneapolis for a pharmaceutical engineers' conference, found the incident frightening.

"You don't hear too much about things like that where I'm from," Larson said. "I'll just have to be more cautious of my surroundings."