heard a pop under the hood while driving, what could it be? on 1990 Chevrolet Astro

yesterday while driving my 1985 astro i heard a small pop under the hood, and then immediately the van shut off and will not start. i think it might be a broken timing belt but im not sure. any ideas?

Asked by for the 1990 Chevrolet Astro
No timing belt on this one. Going to have to get someone to look at it to determine what happened no use guessing.