(a) A person commits an offense if, with the intent to interfere with the lawful custody of a child younger than 18 years, he knowingly entices, persuades, or takes the child from the custody of the parent or guardian or person standing in the stead of the parent or guardian of such child.
(b) An offense under this section is a Class B misdemeanor, unless it is shown on the trial of the offense that the actor intended to commit a felony against the child, in which event an offense under this section is a felony of the third degree.