The Israeli military acknowledged on Thursday that it was responsible for killing a United Nations aid worker in a strike on a UN guesthouse in Gaza last month, backtracking on its previous denials in the face of mounting public evidence of Israeli responsibility.

In a rare apology to the United Nations, Israel said its forces had struck a U.N. compound in Gaza with tank fire. A Bulgarian aid worker was killed.

It was the second time in a week that Israel’s military, after an internal investigation, reversed an initial denial of its role in a deadly incident.