Police arrested 19-year-old Nicholas Felipe on Monday on a charge of aggravated sexual assault of a child.
The alleged incident happened on Dec. 12 after Felipe received a photo of a 16-year-old girl that was in some stage of undress according to police.
"This suspect had made contact with the victim in the case and he threatened to post the picture on a social networking site if she didn't agree to have sex with him," said San Antonio police Sgt. Javier Salazar. "The victim did meet with the suspect at some point and he did forcibly engage in a sex act with our victim."
Police arrested Felipe Monday at a home on the Northeast Side without any problems.
He also faces a charge of indecency with a child by contact for an earlier incident in 2012 involving a 10-year-old boy. Police had an arrest warrant for that crime.