Purged during the Night of the Long Knives, he was able to recover his status, and served as Nazi Germany's Consul in San Francisco between 1936 and 1939. As Ambassador to the Slovak Republic in 1940, he played a part in enforcing antisemitic legislation in that country. In early 1941, Killinger was appointed to a similar position in Romania, where he first became noted for supporting Ion Antonescu during the Legionary Rebellion. Together with his aide Gustav Richter, he attempted to gain Romania's participation in the German-led Final Solution, thus pressuring Romanian authorities to divert focus from their own mass murder of Jews. Killinger oversaw German presence in Romania until 1944, and was the target of a notorious 1943 pamphlet by writer Tudor Arghezi. He committed suicide in Bucharest, days after King Michael's Coup of 23 August 1944 toppled the Antonescu regime.