The last three and a half months have seen near-daily Palestinian attacks on Israeli civilians and soldiers that have killed 24 people.
At least 140 Palestinians have been killed by Israeli fire since mid-September. About two-thirds of them are said by Israel to be attackers, while the others were killed in clashes with troops.
Israel says the bloodshed is fueled by a Palestinian campaign of incitement. Palestinians say it stems from frustration at decades of occupation.
Palestinians have also frequently clashed with Israeli troops in recent months, with protesters throwing rocks and firebombs and troops responding with tear gas and, in some cases, live fire. The 21-year-old was shot dead near the village of Beit Jala, just outside of Bethlehem.
The Palestinian officials initially said the man was 16.