With the case weeks old, the victim's mother, Christina Cherry, is now talking to Action News, pleading for someone to come forward.
Christina Cherry tells us she visits the site of her son's murder every day, and wants to confront the person responsible.
"I just want to know what would make you so angry with him to take his life in such a way?" said Christina Cherry.
The incident happened April 24 in the 1400 block of Vernon Road.
Police say the gunman shot Alex Cherry in the head in broad daylight, only to turn back and shoot him two more times.
"He was an amazing kid," said Christina Cherry. "Always free-spirited, happy, laughing, joking, you know."
Alex had just finished talking to a candidate for state representative, who was campaigning at a corner store. The 21-year-old wanted to volunteer on the campaign.
His mother tells us he planned to work the polls on primary day that week with her.
"There's a lot of witnesses that were out there," said Philadelphia Police Capt. James Clark. "We need someone quite honestly to come forward, and tell us who did the shooting."
In the weeks leading up to Alex Cherry's murder, police say they saw a rise in gang activity and suspect a neighborhood rift.
Hours later, a 17-year-old who knew Alex was also shot to death around the corner on Temple Road where Alex lived.
"We believe that this has something to do with the opposing groups fighting back and forth, and that's the part the investigation is taking us right now," said Capt. Clark.
Christina Cherry says her son got into some trouble in his teens, but was on a different path that now involved church and a bright future.
Alex was scheduled to start technical school the next day.
"I'm never going to be at peace with the death of my youngest child. That's never going to sit right with me," said Christina Cherry. "I am going through a lifetime of torture, but if anybody can help me get through it just a little bit, you know."
A reward for up to $20,000 is being offered for information leading to an arrest.
Christina tells us she hopes to hold a fundraiser so she can add to that cash incentive.