Tips led police to the persons of interest, but authorities were not yet ready to call them suspects in this case, Philadelphia Police Captain James Clark said in a Monday afternoon news conference.
Sources tell Action News at least five people, including those persons of interest, are being questioned by police.
The killing happened at 10:37 p.m. Sunday in the 900 block of North Front Street.
26-year-old Amber Long was walking with her mother when it happened.
Amber's mother Stephanie spoke to Action News on Monday morning, saying she was in town visiting from Harrisburg.
"She was just an extremely talented person who was full of life," Stephanie Long said.
Amber and Stephanie had a mother-daughter girls's night out Sunday night. They attended an art show at the Pennsylvania Convention Center.
Later, they took the El to the Spring Graden Street Station to retrieve Amber's car from her boyfriend's.
They were walking from the SEPTA elevated rail station when they were jumped by two men on the 900 block of Front Street.
"One of them grabbed my purse and got away. The other one tried to grab her purse and she resisted. He shot her; he just shot her at pointblank range. He shot her in the chest and he shot to kill. It went right in the heart," Stephanie said.
Police rushed Long, who lived in the 1700 block of West Ritner Street in Philadelphia, to Hahnemann University Hospital, where she was pronounced dead at 11:15 p.m.
The two robbers jumped into a dark-colored or black Chevrolet Impala driven by another man and disappeared. That car has not yet been located, Clark said.
Police picked up two men matching the description at a house on the 5600 block of Camac Street.
"Through investigation, we've actually received some very good tips. We have two persons of interest upstairs in Homicide now that we're speaking with," Clark said.
Police took two women from the house Monday afternoon and are searching it hoping to find the stolen purse and the gun.
Amber Long was the only child of Troy and Stephanie Long.
She grew up in Williamsport, but fell in love with Philadelphia.
"She moved here to go to school and when she came here for school, she loved the city and she stayed. She wanted to get a job here, so she got a got a job here. She stayed. She loves Philly," Troy Long said.
Amber studied architecture at Philadelphia University and was working for a local architecture firm. She was also an artist.
Her mother proudly showed Action News a series of intricate pen and ink drawings she had been working on.
"She was a beautiful young lady. She had her life together," Stephanie said.
Anyone with information is asked to contact Philadelphia Police at 215-686-TIPS (8477), text a tip to PPD TIP (773847) or through PhillyPolice.com.