Di Matteo took part in the killing of Antimafia judge Giovanni Falcone on 23 May 1992, near Capaci. After his arrest on 4 June 1993, he became the first of Falcone's assassins to become a government witness – a "pentito". He revealed all the details of the assassination: who tunnelled beneath the motorway, who packed the 13 drums with TNT and Semtex, who hauled them into place on a skateboard, and who pressed the button.