Malmö Östra hospital murders
The Malmö Östra hospital murders were a Swedish case of serial senicide committed by the 18-year-old Anders Hansson at a hospital in Malmö between October 1978 and January 1979. Hansson poisoned elderly patients during his working hours as an orderly with the detergents Gevisol (contains sodium hydroxide; undiluted solution has a pH of 12) and Ivisol (contains potassium hydroxide; undiluted solution has a pH of 13).
Source: Wikipedia — Malmö Östra hospital murders (CC BY-SA 4.0)