One could eliminate the warfarin and brodifacoum forms of rat poison, they take time to tie up the vitamin K1 clotting factors and result in death days later from bleeding. The other major rat poison used in the US would cause seizures in a toxic situation. Zinc phosphide poisoning symptoms are consistant with those described along with the rapid mortality. Sodium flouride and ethylene glycol are also possibilities. Arsenicals and heavy metals have symptoms that are consistant with those described. Strychnine, organophosphates, carbamates, and neurotoxins can be eliminated from the descriptions.
IMHO and personal experience, the agent most likely would be zinc phosphide.
What's the mechanism of action of zinc phosphide?
Coumadin analogues create signs and symptoms consistent with the news story (interference with the natural coagulation cascade).
Your point about seizures is a good one, but perhaps the media is not saavy to such things. What arguments were floated to eliminate the other tickets.