After a tragic train accident

[Bassim]

I am wondering if my sentence is grammatically correct.

After a tragic train accident, a stream of injured passengers poured into the city hospitals.

 

[Lynxear]

I would only change "a" to "the" at the beginning.

After the tragic train accident, a stream of injured passengers poured into the city hospitals.

This would make your statement specific to a single tragic event. I like your creative use words here. You are going beyond constructing mundane sentences.