  We present concrete construction of interior operators for a black hole which
is perturbed by an infalling observer. The construction is independent from the
initial states of the black hole while dependent only on the quantum state of
the infalling observer. The construction has a natural interpretation from the
perspective of the boundary operator's growth, resulting from the collision
between operators accounting for the infalling and outgoing modes. The interior
partner modes are created once the infalling observer measures the outgoing
mode, suggesting that the black hole interior is observer-dependent.
Implications of our results on various conceptual puzzles, including the
firewall puzzle and the information problem, are also discussed.
