Korean Political History II: Chapter 6, Exercise 3 — Possible Solution
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SENTENCE
"In 2017 Kim Jong-nam, Kim Jong Un's half-brother, was assassinated in
Malaysia; the sources I read do not say who carried it out or attribute it."

WHY THIS WORKS
It states the reported fact (the killing, the year, the place) and
names what is not established (the perpetrator and the motive). Saying the
leader ordered it would go beyond the sources.