Complex sentence: Weapons were found concealed in a bathroom (in the toilet flush tank) that matched the description of those used by the robber, and ammunition for the shotgun was found in the bureau in Mr Hayden's bedroom, and ammunition for the handgun under his mattress.
Split into simpler sentences: Weapons were found in a bathroom that matched the description of those used by the robber. Ammunition for the shotgun was found in Mr Hayden's chest of drawers and ammunition for the handgun under his mattress.