The peacekeeper, Private Sean Rooney, was killed and three others injured when their United Nations Interim Force in Lebanon (UNIFIL) vehicle was attacked near the village of al-Aqbiyeh, a Hezbollah stronghold.
UNIFIL acts as a buffer between Lebanon and Israel and operates near the border.
“The main shooter has been arrested by security forces after Hezbollah handed him over hours ago,” the security official said, declining to be identified because he was not authorized to speak to the media.
Media reports indicated that the arrested man is allegedly a 31-year-old Hezbollah supporter.
The group is cooperating with the investigation led by Lebanese military intelligence, and the official stated that “preliminary investigations are nearly complete.”
Hezbollah has repeatedly denied involvement in the incident, and its security chief, Wafiq Safa, described the killing as “unintentional.”
Witnesses said villagers in the al-Aqbiyeh area blocked Rooney’s vehicle after it took a road not normally used by UNIFIL. The three passengers were injured when the vehicle hit a pylon and overturned.
Over the years, there have been a number of incidents between Hezbollah supporters and UN peacekeepers, but they have rarely escalated.
UNIFIL has urged Lebanon to ensure a swift investigation into the first violent death of one of its peacekeepers in nearly eight years.
The force was set up in 1978 to monitor the withdrawal of Israeli forces after they invaded Lebanon under the excuse of a Palestinian attack.
The attack on Rooney and his colleagues was met with condemnation from the Irish government and the United Nations.
UNIFIL released a statement condemning the attack and expressing condolences to Rooney’s family and the Irish people. The attack also raised concerns about the security situation in southern Lebanon, where UNIFIL has a mandate to maintain stability.