The United Nations human rights office said the killing of a wheelchair-bound protester by the Israeli military during clashes in Gaza last Friday was a "truly shocking" act.
Ibrahim Abu Thuraya, 29, a Gazan double amputee who lost both legs nine years ago in an Israeli airstrike, was protesting near the Israeli border when he was shot in the head by a sniper last Friday.
An investigation by the Israeli military into the death cleared troops of wrongdoing, claiming it found "no moral or professional failures" in the incident.
Clashes between Palestinians and the Israeli military have flared since Donald Trump declared Jerusalem to be Israel's capital and that he would be moving the US embassy there from Tel Aviv.
Threatens to harm any hopes for peace
The US president's unilateral declaration, welcomed by Israel but condemned worldwide, threatens to harm any hopes for peace in the Middle East, which were already fading after Israel's 10-year blockade on Gaza and its seizing of more land for illegal settlements in the occupied Palestinian territories.
The US angrily blocked a UN Security Council resolution calling for Trump's decision to be rescinded after the other 14 members voted in favour of a motion proposed by Egypt.
US ambassador to the UN Nikki Haley responded: "What we witnessed here today in the Security Council is an insult. It won't be forgotten."
But Trump's declaration only served to confirm what many observers already suspect: The US cannot be an impartial broker in a deal for peace in the Middle East.