It is with great sadness that we announce that our dear friend and colleague Pieter Hofstra (1975-2022) passed away unexpectedly on May 1. Pieter obtained his PhD from Utrecht University, under Jaap van Oosten, studying realizability toposes. His research interests included general topos theory, realizability, inverse semigroups and groupoids, abstract computability, and homotopy type theory. Among his recent works, with J. Funk he introduced the notion of isotropy groups of toposes, which he was actively developing with students and colleagues. While Pieter was a brilliant researcher, a kind teacher and a caring supervisor, we will most remember him as a friend. When we have any details for a memorial service, we will pass them along. Richard Blute, Simon Henry, Philip Scott (University of Ottawa) [For admin and other information see: http://www.mta.ca/~cat-dist/ ]