EAST FLATBUSH, Brooklyn (WABC) -- The man wanted in the fatal shooting of a Brooklyn teenager is now under arrest.24-year-old Taariq Stephens surrendered to police Thursday night. Police say Stephens was caught on surveillance camera with another young female inside the building just prior to the deadly shooting of Shemel Mercurius, who was babysitting her cousin.Stephens is now facing charges of second degree murder and second degree criminal possession of a weapon.Earlier Thursday, police identified Stephens and said he was armed with a submachine gun.Officials released the video, which shows the pair getting into the elevator of the building on Brooklyn Avenue in East Flatbush together, but for unknown reasons, the male gets off on the floor below the shooting while the female gets off on the sixth floor, where the victim lives.The young man then climbs the stairs and emerges on the sixth floor, where the Mercurius is seen in her doorway. When the young man emerges from the stairwell, she closes the door. The male suspect, apparently holding a gun or a rifle, then pushes his way into the apartment, with the young woman following behind him."He pulls out the stock of the gun before he shoots the young lady," NYPD Chief of Detectives Robert Boyce said. "He racks three times, so we get three full rounds outside in the hallway. He shoots her one time, that goes through her arm and into her body. That causes her demise later on at the hospital. We are seeking him now."After the shooting, the pair fled the building, possibly down the fire escape. It all happened around 6 p.m.Mercurius, a student at Edward R. Murrow High School, was rushed to Kings County Hospital, where she was pronounced dead. She was reportedly semi-conscious when EMS arrived and was able to say the name of her killer to police. Her 3-year-old cousin was not injured."She names him, 'Taariq,'" Boyce said. "She does not say it's a boyfriend. From what we can read of the texting, it is not look like a romantic relationship. There's lot more to go in this case, a lot to figure out. We do have him ID'd. We think he is a dangerous guy, especially with that weapon. So we are concerned about it." Emotion poured out Wednesday at a candlelight vigil , where the victim's father, Dexter Mercurius, came to call for justice. But he couldn't bring himself to speak."As we can see, this is a very traumatic day in this community," City Councilwoman Laurie Cumbo said. "When I think of this young lady, I think of myself."Elected officials called for increased gun laws and better funding to help the victims of crime."What society do we live in when a 3-year-old boy can, actually they shot the young lady in front of him?" said Pastor Gilford Monrose, of the 67th Precinct Clergy Council. "And then having to go back in and sleep the same night, he's being re-traumatized over and over again."Her dad is praying someone steps forward and helps police bring in the suspects."Thank you everybody for coming out and supporting my daughter," he said. "Still got to go on, so thank you everybody. Thank you."The Mercurius family released a statement Thursday night saying:Investigators said the motive for the shooting is still not clear. Anyone with information is asked to contact police.