The Irish government said an investigation was under way into the gun attack.
The Irish Defence Forces are sending a specialist team to examine all of the circumstances leading up to the attack.
Their investigation will focus on how the vehicle became separated from its accompanying armoured vehicle.
Pte Rooney’s vehicle entered the village of Al-Aqbieh, where a crowd of locals had been watching Morocco play France in the World Cup.
UNIFIL is also investigating and said it was coordinating with the Lebanese Armed Forces to determine exactly what happened.
Speaking on Friday, Taoiseach (Irish Prime Minister) Micheál Martin warned that getting to the truth would be challenging.
“These investigations have to be very comprehensive – we are determined to get the truth,” he said.
“The environment is difficult, the environment is challenging and, as we know now, with the terrible cost, it’s clearly a tense situation.”
Mr Martin added: “It is a reminder of the extraordinary sacrifice our peacekeepers make on a constant basis.
“They operate in hostile, at times very difficult and dangerous environments and we should be conscious of that.”
Pte Rooney had previously been deployed to Lebanon in 2021, having joined the Irish Defence Forces in 2019.
