I got this shirt along with several others from an estate sale of a 70 year Canadian guy from Ottawa. I tried googling "brigade" and "PNP" and haven't had much luck, but my guess currently is that this guy has something to do with the Philippine National Police? The previous owner was not Filipino
The “3” on the shoulder does feel like it might be a reference to the 3 months thing. It does seem weird having a huge photo of your opponent’s face on you but if these were made for some one-off event, it might explain that, plus why it’s so hard to find any information in hindsight.