Their families spent four frantic days searching until police called on May 12: They'd found a body behind an apartment building in Juniata Park, about three miles north of the Colons' house.
Melanie Colon had been shot six times at close range. Her arms were scratched, her fingernails torn off. Her body was decomposing by the time a man hunting for doves found her.
Reynaldo Torres is still missing.
"For Melanie's parents, it's really sad. I do not dare to put myself in their shoes," said Maria Colon, Torres' mother, who is not related to Melanie's family. "But they already know where their daughter is. I don't know anything. This is an agony."
Philadelphia police say answers are few and far between in the four-month-old case.
Colon and Torres weren't involved with drugs, police said. They had no ties to gangs. They weren't the type, police said, to cross the wrong people. Police still have no leads on who might have killed Colon but they believe her body was moved to the Juniata Park neighborhood where she was found.
Police later found Torres' gold Mazda abandoned near Roosevelt Boulevard but no sign of Torres.
"It's an unusual case, and I've dealt with this stuff for 26 years," said Chuck Greblowski, the Philadelphia police lead detective on the case. "It's just odd. They just dropped off the face of the Earth."
Police are still looking for Torres, considered a person of interest in the case simply because he has not been heard from in months.
In the house on Reese, Ralphiee Colon maintains a shrine of sorts for his sister. A large photo of Melanie hangs above the fireplace. The mantle is covered in photos of the young mother, smirking from behind a curtain of platinum-blond hair, grinning at the camera in an old school photo.
Now 18, Ralphiee devotes much of his time to running a Facebook page dedicated to finding his sister's killer.
"Our time will come, Justice will be served. I'm not giving up at all - that's a big promise Melanie!" he wrote on Monday.
The page has more than 3,500 likes.
To Ralphiee, his older sister was nothing short of a star. The four Colon children spent their early lives shuttling from relative to relative around the city; when their father served a stint in prison and their mother went to rehab, Melanie looked after her younger brothers.
"She wasn't only a sister - she was a mom," Ralphiee said. "She made sure we went to school. She took care of me. She would go crazy if I was to get out of line."
Outside the family, Melanie was a popular DJ in the gay community, spinning at house parties around North Philadelphia under the moniker "DJ Kiss."
When she disappeared, she was raising her 4-year-old son, Josh, at her family's house. She had a boyfriend in New Jersey. She had just a semester left to go before earning her GED.
"Everything was great. Everyone was happy," Ralphiee said. "She was turning into an adult."
Three miles north, in her daughter's house, Reynaldo Torres' mother still can't sleep through the night. Maria Colon got on the first flight from Puerto Rico when she learned her son was missing and hasn't left the area since.
She's waiting, she says, for Reynaldo to come home.
Torres has two daughters, 19 and 14, and was living with his sister near Juniata Park when he disappeared. The mechanic - who worked out of a garage on Reese - was a gentle soul, his mother said.
Once, a coworker, hearing a mouse squeaking in the trash can in their garage, told Torres to kill the mouse and throw out the trash. Torres dug through the garbage until he found the frightened rodent and set it free before tossing the bag into a Dumpster.
"He's not a person to harm anyone, no matter what anyone says," his mother said.
Advocates in the area say that for the families of victims of unsolved murders, the agony of their loved one's death is compounded by the agony of the unknown.
"When the crime goes unsolved, it's this constant thing that stays with our families," said Molly Schamel, an adolescent therapist at the Anti-Violence Partnership of Philadelphia. "They have a new image of what the world is like - that it's not fair, that it's scary, that people do really bad things."
Both families say they're still searching for answers. Last week, thanks to a donation from a member of his Facebook group, Ralphiee began distributing fliers around the neighborhood, asking for leads in Melanie's case and reminding tipsters that the city has offered a $20,000 reward for information.
"It's not fair," Ralphiee said. "My sister's six feet under, and her killer's still on the loose."
Outside the house on Reese Street, family members have affixed a painting of Melanie to a utility pole. They plan to rent a banner asking for tips at the Puerto Rican Day Parade this weekend, hoping someone will see Melanie's face and call the police.
In the meantime, all they can do is wait.
"The only thing we know is that Melanie is dead and we had to bury her," Ralphiee Colon said. "I wouldn't wish this pain on nobody."
Contact Aubrey Whelan at 215-854-2771, firstname.lastname@example.org, or follow on Twitter at @aubreyjwhelan.