The survivor was able to save himself and his family as the terrorists rampaged through his town by locking himself in his safe room with his family and fighting off attempts of the terrorists to get in to murder them all.

He sent a question to Rav Zilbershtein asking if he should make a seuda to thank God for saving him from the horrors, in light of the fact that so many in his community are injured or have been killed and people are suffering so much? He understands he needs to make a seuda to thank God but maybe it is not appropriate now considering his friends and neighbors. He asked Rav Zilbershtein what to do.

Rav Zilbershtein paskened, after some back and forth regarding a relevant gemara, that he does need t make a seudas hodaa but he cannot do it in his home community. People there are suffering, the blood is still flowing, the people are still crying and mourning, it would not be appropriate for him to celebrate there while they are suffering so strongly. Rav Zilbershtein said he should travel to the center of Israel and make a seudas hodaa there for yeshiva boys or avreichim to partake in, or he should even just give out sweets, and thank Hashem for the miracles done for him, while also including some chapters of tehillim and prayers for Israel's salvation

source: Hamechadesh