Visconti was a well-connected official in the Milanese court, and the Duke, although popular as a patron of the arts, was known to be rather ruthless in his rule and something of a womaniser.
On 26 December 1476, the three conspirators met at the church of Santo Stefano Maggiore, the site where the assassination was to take place.
The Duke died during the attack and everyone - assassins included, quickly fled the church except for Lampugnani who was struck down.
Visconti was caught on 29 December, given up by a frightened relative, and was publicly executed on 2 January 1477 along with Franzone and Olgiati.
The bodies of these three men were torn from groin to neck and affixed to the gates of Milan as a warning to others; the heads separated and displayed on lances on the city's belltower.