What type of event happens at the beginning of the first "Godfather" film?

"The Godfather" (1972) movie is set in the 1940s and takes place entirely within the world of the Corleones, a fictional New York Mafia family. It opens inside the dark office of the family patriarch, Don Vito Corleone (also known as the Godfather and played by Marlon Brando), on the wedding day of his daughter, Connie (Talia Shire).

Vito’s youngest son, Michael (Al Pacino), who has distanced himself from the family business, attends the festivities with his non-Italian girlfriend, Kay (Diane Keaton). A few months later, Vito is nearly killed by gunmen sent by a rival family, and Michael saves him from another attempt while he is recovering in the hospital.

Michael then takes revenge, killing a corrupt police captain as well as the man who ordered the hit on Vito, after which he flees to Sicily as a gang war breaks out. Vito’s eldest son, Sonny (James Caan), is gunned down, and the violence eventually reaches Michael when his Sicilian wife is killed during an attempt on his life. Michael returns home and marries Kay, and Vito makes peace with the rival families. Michael succeeds his father as don, and, after bringing prosperity to the family, he launches a campaign to systematically wipe out all those who had ever attacked the Corleones.