Now, police are on the hunt for that man, Sergio Santiago, who only a few months ago was welcomed into Flores' house when he had nowhere else to go, who was fed by the teen's grandmother when he was hungry.
"Whatever Joey had, he shared with him," said Antonia Flores, who raised her nephew as her son. "I treated [Santiago] just like another son."
Court records show that Santiago has had multiple brushes with the law, including a guilty plea for armed assault in June 2012. He spent a few months in Curran-Fromhold Correctional Facility last year during a criminal trial for drug offenses, but those charges eventually were dropped and he was released.
So, last September, he paid a visit to his old friend Joey - a kid who police say never had any brushes with the law - looking for a place to stay.
"I didn't like the idea, but I said yes, because they were so close," Flores said. "I was afraid Joey might get into some trouble, hanging around with him, but I never passed the thought that he would hurt Joey.
"Now, in my eyes, he's a monster because he killed my son."
Exactly what transpired Sunday afternoon is unknown, but Flores' family shared what little they knew: Four men, including Santiago and Flores, were in an apartment on the third floor. One shot was fired, and it struck Flores in the head. The other men fled, and one of the building's residents called police when they heard the commotion.
A half-hour later, Flores died at Hahnemann University Hospital.
"He was an inquisitive kid, impressionable," said Daniel Aviles, Antonia Flores' ex-husband. "He was looking for a big-brother type, someone to look up to.
"But, unfortunately, this is what took care of him," Aviles said, gesturing to the streets on which Flores grew up. "This neighborhood is filled with kids being raised by kids."
After losing his parents, Flores struggled to find a role model, Aviles said. He became "mesmerized" by Santiago, a tough, swaggering kid who defied authority. Yet despite his friend's rough reputation, Flores stayed out of trouble with the law; Officer Jillian Russell, a police spokeswoman, said his record was spotless.
"He wasn't a thug or a hoodlum," Wendy Aviles, Antonia Flores' daughter, said of Joey, her adopted brother. "The environment you're around affects who you're becoming."
Aviles described her brother as a kind, gentle teen who loved animals and cared for reptiles, dreaming of one day opening his own zoo.
"He wanted to see good in everyone," she said. "People were drawn to him, took advantage of his kindness."
To hear Daniel Aviles Jr., Flores' adopted brother, tell it, one such person was Santiago,
"I knew that kid was trouble since day one," he said. "He gave off a bad vibe."
Aviles tried to warn his brother to stay away from Santiago, but his advice fell on deaf ears.
"They knew each other since they were toddlers, even though Joey knew he wasn't right for him," he said. "That's who he felt comfortable around."
The environment was anything but comfortable last night on Wallace Street. Steps from the door to the building where Flores was killed was a memorial to the slain teen, complete with teddy bears, votive candles and handwritten messages from friends.
A tearful Antonia Flores hugged family members, their faces illuminated by the candles.
And, when asked about the man now being sought by police in her son's death, her face hardened.
"God forgive him," she said, "because I can't."
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