Background: Natan-Zada was born to an Israeli-Jewish family that had immigrated to Israel from Iran and Yemen. Natan-Zada's parents describe him as having been a "bright and studious Israeli schoolboy" prior to his becoming involved with the Jewish extremist Kahanism movement, to which he was introduced via the Internet. He then began spending weekends in Kfar Tapuach, an Orthodox West Bank settlement. During his national service in the Israel Defense Forces (IDF), Natan-Zada deserted the army and hid in Kfar Tapuach to avoid further service.
Context: The Israel Police opened a criminal investigation into Zada's lynching. The High Follow-Up Committee for Arab Citizens of Israel called on the government to refrain from investigating the death of Eden Natan-Zada. Arab Knesset member Mohammad Barakeh, a Shefa-'Amr resident himself, warned that protests could erupt if police probe Zada's lynching: "Normally when someone stops a terrorist from continuing to kill he is considered a hero, but in this case it is the heroes who are sitting on the defense stand". However, Shefa-'Amr's security officer, Jamal Aliam, told Army Radio that Zada had been attacked by dozens of people after he had been handcuffed and subdued by police. Eventually, on 13 June 2006, five suspects in the lynching were arrested, one who was already serving a prison sentence was brought in for questioning, and a seventh suspect turned himself in after learning he was wanted by police. The police said: "We're responsible for maintaining the law, and you can't take the law into your own hands even when it concerns a terrorist who murdered innocent people, even though he made a heinous terrorist act". Two suspects were subsequently released. There was general support for their arrest and even left-wing activist Yossi Beilin said: "Israel can't put up with a lynch made on a handcuffed person even if his actions are heinous and unforgivable. It's a combined interest of both Jews and Arabs that Israel won't close its eyes to such behaviour". The Arab Knesset members however demanded their release and called their arrest a crime. On 7 June 2009, twelve Arab citizens were indicted over the lynching in the Haifa District Court. Seven were charged with attempted murder. In March 2010, Maher Talhami, their defense lawyer, stated that recently discovered aerial footage of the bus, recorded by an Israeli drone before, during and after the attack took place indicates that Israeli defense officials were aware of Natan-Zada's intentions. In July 2013, the seven defendants charged with attempted murder were acquitted of that charge, but four were convicted of attempted manslaughter and two were convicted of aggravated battery, while one was exonerated entirely. The sentencing took place on 28 November 2013. Three were sentenced to two years in prison, while one was sentenced to 20 months, one to 18 months, and one to 11 months.
Question: What was the investigation about. Whats the answer?
Zada's lynching.