Headlines grammar. Doesn’t work like regular English. It’s designed to be especially concise.

https://englishlessonsbrighton.co.uk/8-grammar-rules-writing-newspaper-headlines/

Replace conjunctions with punctuation

• Police arrest serial killer – close case on abductions

• Fire in bakery: hundreds dead

As with reporting speech, commas, colons, semi-colons, hyphens and so on can replace all conjunctions, or some joining verbs, to join clauses. Commas may also be used to join nouns (more common in American English).

• Man kills 5, self 

I’ve seen a lot of English-as-a-second-language Europeans puzzled by it on Reddit. I don’t know of a single, comprehensive resource that defines it; I just grabbed the above link as an example that lists some differences, and the bit talking about the peculiarity here.