By Steve Patterson and Elizabeth Hur

PHILADELPHIA (CBS) — Police have identified a man they are looking for in connection with the shooting death of a Philadelphia teen.

Eyewitness News has learned he is no stranger to the victim and his family.

Philadelphia Police announced Monday night they are looking for 23-year-old Sergio Santiago in connection with the shooting death of 17-year-old Antonio “Joey” Flores.

“They grew up together. Joey looked at him as a brother,” the victim’s mother, Antonia Flores said.

Eyewitness News is told Santiago befriended Flores years ago when in need.

“Sergio had no place to stay for a little bit, you know, and Joey asked me, ‘Mommy can he stay for a little,'” Flores said.

Family and friends still in disbelief consoled one another all day and night on Monday.

It was Sunday afternoon police found Flores shot in the head in the third floor apartment in the 1600 block of Wallace Street (See Previous Story).

Loved ones held a vigil in Philadelphia’s Fairmount neighborhood Monday afternoon to remember the young shooting victim.

“I love him. Wish he was here, he means a lot to us and the neighborhood,” a neighbor said.

“This is testimony of who he was – testimony of how many people loved him,” the victim’s sister Wendy Avilez said.  “He was honest. He was loyal. He was a good kid. He didn’t start problems with anyone,” Avilez said.

His sister says the most frustrating thing, nobody knows why.

“I’m broken… I’m broken,” Avilez said.

What led to the shooting remains under investigation, but police believe there were other people in that room when the shooting occurred. Police, along with family members, are begging those with answers to do the right thing and call the police.

“Because yesterday it was my son. Tomorrow it could be somebody else,” the victim’s mother said.

Anyone with information on the whereabouts of  Santiago is asked to contact Philadelphia Police at 911 or 215-686-TIPS.