While insisting the attack was an act of terrorism, he acknowledged there were "other factors involved as well", without elaborating.
The IDF said Sunday that Na'alwa was known to security forces but had no past terror offenses and no formal ties to terrorist groups, saying it appeared to have been a "lone-wolf attack".
Security forces launched a manhunt for the shooter, who fled the scene after the attack.
A woman aged 54 was also found wounded, the medical services said.
Israeli Prime Minister Benjamin Netanyahu condemned the attack and vowed deal with the "reprehensible murderer" to "the fullest extent of the law".
He was certain the perpetrator would be caught and brought to justice.
Hamas, the militant group that controls the Gaza Strip - the other main Palestinian territory - called the attack a "heroic operation".
Israel's President Reuven Rivlin and U.S. ambassador David Friedman both condemned the shooting in the Barkan industrial zone, where thousands of Palestinians and an equal numbers of Jewish Israelis have worked side-by-side for decades, as an attack on coexistence.
Critics - many of whom have pushed to boycott the industrial zones - say Israel is taking advantage of a vulnerable workforce and a Palestinian economy crippled by Israeli restrictions.
Palestinians often face tough choices in finding employment in the economically struggling West Bank and jobs in Israeli settlements can provide steady income.
The assailant, the army said, had worked in a factory where the shooting took place on Sunday.
Speaking at Barkan, Yossi Dagan, head of a regional council for Israeli settlements in the area, said there were "Jewish and Palestinian workers standing outside together and crying".