Popper, a former dishonorably-discharged soldier, put on his Israeli army uniform on 20 May 1990 and asked men waiting at a bus stop in the Israeli town of Rishon Lezion for their identity cards. After confirming they were Arabs he lined them up and opened fire, killing seven. Within an hour, he was arrested by Israeli police.
After his act, riots by Palestinians led to the deaths of seven more Palestinians at the hands of Israeli security forces, with 700 injured.
Israel Radio reported that Popper claimed to have been distraught because his girlfriend had decided to leave him. Later he told police that he had been raped by an Arab when he was 13 and had committed these killings out of shame and a desire for revenge.
Popper was charged and convicted of seven acts of murder in March 1991. In prison he became religious and in June 1993 he married a Canadian woman from a family of Kach activists. They had three children.
In February 1999 Popper's sentence was commuted from seven life terms to 40 years. Currently he is expected be released on parole in 2023, after 33 years in prison [according to who?].
On 17 January 2007, while on a 48-hour furlough, Popper was involved in a car accident caused by him crossing a solid line. His wife and one of his sons were killed in the accident. Popper himself was moderately injured. Israeli police reported that Popper's license had expired in 1999.  In December 2008 he remarried. Right wing and Orthodox politicians in Israel have demanded his release along with other Israeli prisoners who were convicted of murder or other violence committed against Palestinians, in exchange for the release of Palestinian prisoners who committed murder or violence against Israelis.