Upset that money was being squandered on public extravagance, the soldiers began to riot.

“In fact they did not cease their rioting until Caesar suddenly came upon them, and seizing one man with his own hands, delivered him up to punishment. So this man was executed for the reason given, and two others were slain as a sort of ritual observance. The true cause I am unable to state, inasmuch as the Sibyl made no utterance and there was no other similar oracle, but at any rate they were sacrificed in the Campus Martius by the pontifices and the priest of Mars, and their heads were set up near the Regia.”

Cassius Dio (XLIII.24)