SHARYGIN 2023 Problem 16

Let $AH_A$ and $BH_B$ be the altitudes of a triangle $ABC$ . The line $H_AH_B$ meets the circumcircle of $ABC$ at points $P$ and $Q$ . Let $A'$ be the reflection of $A$ about $BC$ , and $B'$ be the reflection of $B$ about $CA$ . Prove that $A',B', P,Q$ are concyclic.