A former teacher of Seán Rooney's has remembered him as a great young man with a full life ahead of him.
The Defence Forces Private was killed on Wednesday while travelling to Beirut with colleagues in Lebanon.
The 23-year-old was from Newtowncunningham in Co Donegal.
Damien McCrory is principal of St Eunan's College in Letterkenny, where Seán went to school.
He told The Hard Shoulder the community is devastated.
"We were devastated to hear this news this morning," he said.
"There was a sense of shock and utter disbelief among the school community here that one of our past pupils had passed away so tragically.
"He was a great young man, he had a full life ahead of him.
"He was always a very positive attitude, he's remembered fondly by all staff here in the school.
"We're just devastated to hear this news today."
Private Seán Rooney. Picture: Irish Defence Forces'He fitted in so well'
Mr McCrory said he has very fond memories of Séan.
"I taught Seán myself when he was in the school, so I did know him and I have great fond memories of him," he said.
"He joined us in Transition Year and he fitted in straight away.
"He was willing to get involved - it's always tough joining a new school... but it was as if he was here from the very beginning, and he fitted in so well".
He said a number of past pupils have gone to serve in the Defence Forces.
"When I saw, I think the first maybe came through just after 6 this morning that someone had passed away, that was the first thing I thought of," he said.
"We have a number of boys that would have gone that route and will continue to go that route probably.
"That was the first thing that popped into my head, but then it became a reality at about 11 this morning that the news started to break that it was one of our own".
He added: "These boys are so passionate about going into the Army and give so much dedication to it, and Seán was no different.
"It was something that he was very passionate about and something that he did want to do."
Tributes
Private Shane Kearney, from Killeagh in Co Cork, was seriously injured during the attack and is being treated in hospital.
Speaking from Brussels earlier, Taoiseach Micheál Martin said everyone had been "deeply shocked" by the news.
"It is a reminder to us of the extraordinary sacrifices that our peacekeepers make on a constant basis," he said.
"They operate in, at times, hostile and very difficult and dangerous environments and we should always be conscious of that."
President Michael D Higgins said: "As President of Ireland and Supreme Commander of the Defence Forces, it is with a heavy heart, and conscious of the great loss it will represent to them, that I offer my deepest condolences to the family, colleagues and friends of the member of the Defence Forces who has lost their life.
"A life lost serving the people of Ireland, serving the United Nations, and serving all those wishing for peace in our shared world.
"May I also wish a speedy recovery to those other members of the Defence Forces injured in the incident. Our thoughts are with them at this time."
A senior Hezbollah official has offered condolences for the "unintentional incident" and told Reuters the armed group was not involved.
