Whoever, having knowledge of the actual commission of a felony cognizable by a court of the United States, conceals and does not as soon as possible make known the same to some judge or other person in civil or military authority under the United States, shall be fined under this title or imprisoned not more than three years, or both.
For anything to do with children, quite a few professions are mandated reporters including LEOs, all public and private school personnel except volunteers, social workers, and several other rather large fields. Depending on the state that list expands considerably. Even the clergy of religious institutions are included in 27 states, superceding confidentiality.
Other than LEOs, mandated reporting for general crimes depends largely on state laws except for fiduciary duties.