What the hell is going on???

Ok something creepy is happening at my house. On Monday one of my Canaries(Redband) died. I thought that the other Canary (Bluey) in the same cage attacked it. But today I came home to find Bluey in the cage also dead. I did a quick inspection of the Bluey a couple of hours ago and it had a what appeared to be a circular wound in it's chest. Kind of resembling a small bullet entry wound.

There was no damage to the cage and the birds were quite healthy. I don't know when they passed as I was at University when it happened. I have another cage with 3 budgies which have not been hurt in any manner. Both bird cages are left on a 1st story balcony with secure fencing and a Jasmine vine which provides additional height on top of the fence  I have a dog but she can't reach the cage unless she looses 10 kilograms and cuts her skull in half.

What the heck is going on? I really hope that my Budgies are going to be ok.

RIP Redband (2012-2013) and Bluey (2012-2013).

Any ideas on what it is?
A

RIP Redband

Came home after a long day at uni to find one of my canaries had died. So sad. Even though Redband was only with us for 5 months, I already miss seeing her cute little face and hearing her little chirps. I know Canaries aren't that great with human interaction but it is/was routine to take care of Redband along with Bluey (Canary), Shari, Bunny and Bear (Budgies) in the morning.

Miss you little pal.
A