Hellenistic period:

Meleager and the infantry supported the candidacy of Alexander's half-brother, Philip Arrhidaeus, while Perdiccas, the leading cavalry commander, supported waiting until the birth of Alexander's unborn child by Roxana. After the infantry stormed the palace of Babylon, a compromise was arranged – Arrhidaeus (as Philip III) should become king, and should rule jointly with Roxana's child, assuming that it was a boy (as it was, becoming Alexander IV). Perdiccas himself would become regent (epimeletes) of the empire, and Meleager his lieutenant. Soon, however, Perdiccas had Meleager and the other infantry leaders murdered, and assumed full control. The generals who had supported Perdiccas were rewarded in the partition of Babylon by becoming satraps of the various parts of the empire, but Perdiccas' position was shaky, because, as Arrian writes, "everyone was suspicious of him, and he of them".

Please answer a question about this article. If the question is unanswerable, say "unanswerable". Who documented that Perdiccas' was under suspicion?
Arrian