Short answers, pulled from the story.
David Rizzio was born in Pancalieri near Turin to an ancient noble family known as the Riccio Counts of San Paolo e Solbrito. He arrived in Scotland during 1561 as part of a diplomatic embassy led by Carlo Ubertino Solaro, Count of Moretta.
Mary Queen of Scots had brought musicians from France who needed a bass singer for their quartet so David Rizzio filled this gap and became one of the royal chamber musicians alongside Adrian Lefeau and John Adesoun. His musical role eventually evolved into something far more significant than mere entertainment and he gained wealth under Mary's patronage to become her secretary for relations with France towards the end of 1564.
Lord Darnley discovered rumors that Mary treated David like a lover rather than a servant and resolved to be revenged on the Italian secretary. Patrick Ruthven led rebels into the supper room where guards were overpowered throughout the palace and after a violent struggle David Rizzio was dragged through the bedchamber into the adjacent audience chamber where he received fifty-seven dagger wounds before his body was thrown down the main staircase nearby.
Robert Melville reported from London that Morton Lord Ruthven Lord Lindsay William Maitland of Lethington James Balfour John Bellenden and others had fled after the murder. Elizabeth I asked Sir John Forster to tell these men to find refuge outside England while advocates proclaimed some suspects rebels who had fleeing making it unlawful to help them by the 8th of June.
John Carradine played Rizzio in the 1936 RKO picture Mary of Scotland while Ian Holm portrayed him in the 1971 film Mary Queen of Scots. Andrew Shaver took the role on The CW network television show Reign before Ismael Cruz Córdova starred in the 2018 film Mary Queen of Scots and Tadeusz Pasternak appeared as the secretary in the BBC mini-series Gunpowder Treason and Plot.