Green’s Dictionary of Slang

an excl. used to signify the end, a completion.

1977		C. McFadden Serial 32: That was that — finito.
1989		(con. 1950s–60s) in G. Tremlett Little Legs 179: If people don’t turn up on time, that’s it. Finito.
1993		G. Disher Deathdeal [ebook] ‘If you’re in with Van Fleet, that’s it, finito’.
1998		(con. 1960s) G. Washington Blood Brothers 24: Finito, kaput, ended baby.