No, it's not an Alfred Hitchcock nightmare, it's springtime, and the birds are keeping busy.
You may notice birds attacking your windows in these next few weeks. They have not lost their little bird brains, although it may seem that way to you. The male birds are seeing their own reflection, and attacking what they think is another bird in their territory.
What can you do? We have window decals in the shape of hawks that may help scare them away. Or "scare tape", which flutters in the wind and helps block their reflection. Anything you can put on or in front of your window that will block their reflection (but they won't get their feet caught in) will usually work--bridal veil fabric, bedsheets, bamboo stakes.
Luckily, the nesting season only lasts for a few weeks and the birds should be back to normal.