Magen David Adom emergency medical services said their medics had entered a building at Barkan where they found a man and a woman without pulse, and pronounced them dead.
The woman, 54, was taken to hospital, where her condition was stabilised.
IDF spokesman Brig Gen Ronen Manelis said the Shin Bet internal security service had concluded that the attack was an act of terrorism, but added that the gunman might have had "additional motives" that were not nationalistic. The source said PA security officials believed Na'alowa would prefer to hand himself over to them out of fear he may be killed during Israeli attempts to arrest him or due to a belief that the PA would not hurry to turn him over to Israel.
He was certain the perpetrator would be caught and brought to justice.
On Sunday, the Palestinian Islamist group Hamas praised the attack, calling it a "message to young people of the West Bank and Gaza who are under siege".
The suspected assailant worked at the park, which employs both Israelis and Palestinians.
Israeli captured the West Bank in the 1967 Six-Day War.
Israel's President Reuven Rivlin and USA 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.
"No way in our industrial zone", he said, describing an atmosphere of camaraderie in Barkan".
The attack took place at the Barkan depot of the Alon Group, which manufactures recycling and environmental products, according to Eran Bodankin, a manager at the site.
In a separate operation in the village of Beit Sira near Ramallah in pursuit of a terror financing ring, IDF troops overnight Monday-Tuesday uncovered thousands of shekels in cash that the army said were meant to fund terror networks in the West Bank.
Israel settlements are considered illegal under worldwide law and major stumbling blocks to peace as they are built on land the Palestinians see as part of their future state.