CAMDEN (WPVI) -- Police have arrested the man who family members say shot and killed his mother in Camden.The investigation revealed the alleged shooter was 22-year-old Pedro Mercado of Camden, who is the son of Iris Sanchez.Mercado was arrested at approximately 8 p.m. Friday near the intersection of Haddon and Benson streets.The shooting happened just after 5 p.m. on the 1100 block of North 18th Street.It is unclear what led up to the shooting, but neighbor Samir Jackson says he raced outside when he heard a gunshot."I saw her running back and fourth crying, so I ran outside. I'm like, 'What happened?' She said, 'Pedro just shot my mom,'" said Jackson. "I didn't see him. He was long gone."Neighbors say 38-year-old Iris Sanchez was shot, and sat on the steps until paramedics arrived.She was rushed to Cooper Medical Center where she was later pronounced dead.After the shooting, witnesses say Pedro Mercado drove off, possibly into Philadelphia."He was nice though. We always used to speak. I never thought he was that type of person to do what he did to his mom," said Breanna Cozart, neighbor."As far as I know, him and his mom have always been on rocky terms," said Loresha Gaines, whose sister has a child with Pedro Sanchez.She says she didn't expect the strained relationship would escalate to this."I was just talking to him, and he was telling me how he wanted to look for a job, how he wanted to find a job, how he wanted to go visit my nephew," said Gaines.At the hospital, police questioned a woman who claimed to have spoken with the alleged shooter after he fled the scene.Family members called for Mercado to turn himself in before anyone else was hurt."I'm afraid by him shooting his mother in the stomach, which the cops feel as though he has a weapon, they might just shoot on sight without asking questions first," said Gaines.