Yeah it just looked odd. like I should pause at an inappropriate place.

AP style calls for avoiding state abbreviations in headlines. I don't think "Ont." would be allowed. However, the rule regarding this has this in it: "Other state abbreviations retain periods: Ga., Ky., etc." I guess comma-period is perfectly fine with AP.

AP is crazy.

Any AP experts here? MLA wouldn't do this. AP has tons of weird rules that aren't grammatically correct for sentences, but they aren't sentences - they're headlines.

 "Police holding back details on London, Ont., attack on Muslim family for good reason, chief says"

What are the rules for the comma after the period for the provincial abbreviation? What would your alternative be?

Is there an extra comma in this headline?