Aden Devlin loved to earn money.

Whatever the 7-year-old made, he shared with neighborhood kids, his family said Monday.

He earned spending money doing what he called "his job," selling candy to passengers on SEPTA's Broad Street Line. Some riders came to know him as a familiar face.

But about 6 p.m. Sunday, Aden, of Strawberry Mansion, slipped while moving between subway cars near the North Philadelphia station at Lehigh Avenue and fell onto the train tracks, where he was struck and killed by another car, Philadelphia police and transit authority officials said. He was pronounced dead at the scene.

The National Transportation Safety Board launched an investigation into the accident Monday. The NTSB will work with SEPTA and Philadelphia police, who are conducting a joint investigation. SEPTA Transit Police Chief Thomas J. Nestel III said the investigation was standard procedure after such a death.

At the time of the accident, Aden was with his 11-year-old brother and an adult family friend, 26-year-old Jahras Edwards.

Family members said that the trio began moving between cars while the train was stopped but that Aden dropped candy on the way. When he went to retrieve it, the train began moving and he slipped. His brother tried to grab him and Edwards tried to grab them both but was not able to save Aden, the family said.

Kimberly Dantzler, 29, and Troy Devlin, 36, hold a poster of their son, Aden Devlin, 7, who died after falling from a SEPTA subway train while walking from one car to another.
DAVID SWANSON / Staff Photographer
Kimberly Dantzler, 29, and Troy Devlin, 36, hold a poster of their son, Aden Devlin, 7, who died after falling from a SEPTA subway train while walking from one car to another.

Edwards said he took the first grader to sell candy most days after school dismissal at Dr. Ethel D. Allen Promise Academy and also on weekends, as he did with many other neighborhood children.

"I loved all the kids," Edwards said Monday through tears. "I just wanted to help them."

Taking them to sell candy was a way to show "them how to make money without doing illegal stuff, at a young age," said Troy Devlin, Aden's father.

For Aden, selling candy was "all he was thinking about," Troy Devlin said. He started selling candy at 4 years old at 69th Street and graduated to the subway earlier this year.

Aden's family and friends gathered Monday evening at Broad Street and Glenwood Avenue for a candlelight vigil,  where they carried signs and released blue, white, and red balloons, a tribute to Aden's "work" outfit —  blue pants and an alternating white or red shirt.

After the candles were lit and his mother, Kimberly Dantzler, said a few words, a song was played — "I'll Be Missing You" by Faith Evans — and the balloons were released into the night sky.

Among the group of roughly 60 friends and relatives were some of Aden's closest friends.

"He was my best friend ever," said Nakai Davis Carter.

"That used to be my bestest cousin. We used to always play at his house," Lemaj Hardwick said.

Another friend, Solei Miles, said Aden used to be better than anyone at the monkey bars. "He taught me how to play on the playground," she said.

Youngsters gather at a vigil for Aden Devlin, 7, who was killed Sunday while walking between subway cars.
Matthew McCann / Staff
Youngsters gather at a vigil for Aden Devlin, 7, who was killed Sunday while walking between subway cars.

Earlier in the day, cousins, aunts, uncles, and extended family packed into a relative's home in Strawberry Mansion, where they remembered Aden, "a true hustler," for his style, work ethic, and joy.

In the middle of the living room, a family member colored "R.I.P. A" on a red poster for the vigil.

"He touched everybody in their own individual way," said one cousin passing through the living room, noticing the sign.

"He was an Avengers boul," Troy Devlin said.

Dantzler sat in a corner quietly. Since Sunday night, she has listened to "Photograph" by Ed Sheeran on repeat, a song she played for Aden as a toddler.

"My son was a fighter," Dantzler said. "Best thing I ever did was give birth to a strong boy."

Juanita Walker, known as "the water ice lady," remembered how Aden earned money so he could buy what he wanted — sometimes water ice, sometimes sneakers. "He was one of those good kids," Walker said.

Some wondered about safety on SEPTA.

Safety should be SEPTA's priority, said Theresa Guyton, Aden's cousin.

The platform between cars has three chains on both sides that act as a barrier to protect those passing through. Aden fell off the platform despite these protections.

"Why doesn't SEPTA make it more safe by locking those doors when the train is in motion?" Guyton said.

At a news conference Monday, James Fox, SEPTA's assistant general manager for system safety, said it has no immediate plans to change the physical make-up of the gangway, but is open to modifications that would improve safety.

James Fox, SEPTA’s assistant general manager of system safety, speaks during a news conference Monday, Sept. 24, about Aden Devlin, 7, who died Sunday after falling from a subway train.
DAVID SWANSON / Staff Photographer
James Fox, SEPTA’s assistant general manager of system safety, speaks during a news conference Monday, Sept. 24, about Aden Devlin, 7, who died Sunday after falling from a subway train.

"We are always looking for continuous improvements in our systems. …We're going to look at all the options and see what's available," Fox said.

Regardless of the outcome of the investigations, Troy Devlin said, no one is to blame for what happened to Aden.

"It was just an accident," he said, "and I don't want people to judge [Edwards] like he was a bad guy."

Staff writer Kristen A. Graham contributed to this article.