Brandon Conrad, 14, of the 4600 block of Oakmont Street; Malik Page, 16, of the 4700 block of Oakmont Street; and Emmanuel Harris, 17, of the 4400 block of Shelmire Street are charged murder, robbery and related offenses.
The victim, 57-year-old Kevin Cullen, died after the attack on the evening of Sunday, November 25.
Officers were called to the 4200 block of Loring Street for a robbery and arrived to find Cullen lying on the ground unconscious. He died at the hospital the following day.
The seconds before the brutal beating were recorded by a home surveillance video camera. The video shows Cullen being followed before he was attacked out of frame.
"They were laughing, like it was funny," one resident told Action News last week. "They hit his head into a wall so hard I felt it in my house on the second floor."
VIDEO: Surveillance video recorded moments before the attack
On Monday the head of the Philadelphia police department's homicide unit said he thinks young people see these robberies as a right of passage.
"We know and we've confirmed through the investigation that the motive was robbery. Mr. Cullen's pockets were turned out and other items in the investigation led us to that as well," said Capt. Jack Ryan.
However, Ryan said, nothing was ultimately taken as Cullen did not have anything in his pockets.
The three suspects are friends who attended Lincoln High School, police say, and investigators are now looking to see whether they are involved in another assault for which a friend of theirs is already in custody.
Tom Cullen said his brother had no permanent address and would stay with various people.
57 year old Kevin Cullen fatally assaulted in Mayfair. His family says he was the 4th of 6 siblings, was deeply loved and is very missed. Search for teen suspects continues. pic.twitter.com/dYWRHycSm7— Katherine Scott (@KScott6abc) November 28, 2017
Tom said since their father passed away 11 years ago, Kevin had a particularly difficult time and had his demons. But Tom said he was always in his family's hearts.
"We didn't get to see him too often. He would come in and out of our lives," Cullen said. "He was not abandoned, he was not unloved. He was loved deeply."