Eighteen-year-old Siohban Lee met her killer through a social network site, according to D.C. police.

The Takoma Park teenager told friends last week that she was planning to meet a man she met on the Internet, according to charging documents released Monday.

She wound up fatally shot in the head about 3:30 in the morning in Northwest Washington. Her iPhone was missing.

Detectives and wireless company officials tracked the phone to an apartment at 323 Kennedy St., just three blocks from where Lee had told her friends that she was going to meet her new friend.

It was there, that investigators encountered the man whom Lee had met online, 21-year-old Alexander Buckley. At first Buckley denied knowing Lee, police said.

But when he showed police his own cellphone, the device indicated that it was used to call Lee's phone, police said.

Buckley changed his story, and led police to a closet where they found Lee's iPhone in a shoe.

Buckley told detectives that he bought the iPhone and a iPod earlier that morning from a black male. He said he didn't know the name of the seller.

Eventually, Buckley told investigators that he connected with Lee through a social media application called Tagged.

He said he and Lee frequently contacted each other through Tagged. He said he was trying to meet her so he could have sex with her, but the two never met.

When asked to explain how he got her cellphone, Lee said it was "mere coincidence that he knew the decedent and he had her stolen iPhone," court documents said.

Police said Buckley changed his story again, saying he heard the gun shots and was near the site of the Lee's shooting, and saw the victim on the ground but did not realize it was Lee. He saw the iPhone on the ground, picked it up and left.

Police issued a search warrant at Buckley's residence and recovered several other cellphones and a 9 mm handgun.