Question about a cat that just passed away in neighbors yard?

ok so my neighbors have been seeing a stray cat come in and out of there yard well today they found him in the corner of there garage he was hissing every time they got close to him and he was panting hard like he was having a heat stroke or something but then he moved and layed down somewhere else then she went to check on him cause she thought he was ok but then he started meowing like he was hurt so she tried to help him and he hissed at her really loud then he started panting really hard he was almost like drooling it looked like saliva then she told me that it started just pouring out of his mouth then it started to turn colors like a brownish color almost then he got to where he was bearly breathing and it looked like he was having spasms in his chest to stomach area when he breathed which was shallow then all of a sudden out of no where he started gushing blood out of his chest hear his little arm she ran in to get a towel while i was on the phone with the vet but when she picked him up he passed away in her arms but he didnt have a puncture wound or anything and wasnt bleeding at all until he took one of his last breaths so im wondering what could have happened to him?? it looks like something ate there way out from the inside cause like i said he was bleeding or anything he just started gushing blood could he have been posoined or has anyone seen this before???