He was also instrumental in convincing Octavian to pardon Gaius Sosius, one of Mark Antony's generals, after his capture.
His wealth made him a target in the proscriptions of the Second Triumvirate, which he evaded by arming his clientes and slaves then fighting his way to the Italian coast, from whence he sailed to join the forces of Sextus Pompeius.
[3] At some point after the Pact of Misenum was concluded in 39 BC, Arruntius was one of several Pompeians who switched sides and became a supporter of Octavian.
A Lucius Arruntius is also mentioned in Seneca's Epistulae morales ad Lucilium as an imitator of Sallustius' literary style and as the author of a historical work on the Punic War.
He had a son, Lucius Arruntius, consul AD 6, who played a prominent role in the Senate after Augustus died.