Over the years I have seen a few odd things but this one made me jump. The pigeon flew straight into the window with a loud thump and then flew off.
I've experienced something like this with a Robin during the Spring mating season 6-7 years ago, where it's reflection must have been taken as a rival male. After a day or so, and plenty of day time banging against that window, the attacks ended, with no bird (or reflection) apparently harmed. A dark interior, plus double pane windows, enhances outside reflections.
Unfortunately this is a regular occurrence at my house which has large windows. Mostly wood pigeons but, sadly, on one occasion a kingfisher.
Used to happen a lot in our house - after all kinds of contraptions (like strings with feathers), we put up Window Gel Clings... I did not think it would work (and it does look a bit childish), but I think it has happened only once since.
I love kingfishers. I know this is OT but as a kid my dad and I pretty much lived in a canoe, paddling down creeks, rivers, and bayous. Very frequently a kingfisher would be just ahead of us perched in a tree. As we would approach it would fly down the narrow waterway some distance an perch in another tree. This would repeat throughout the day, as though the kingfisher was guiding us down the channel. It happened all the time yet never lost the magical feeling of being guided through the watery wilderness by a kingfisher.