I have seen that behavior too among Northern Cardinals.

Blue Jays can be very aggressive. From All About Birds: Blue Jays

• Blue Jays are known to take and eat eggs and nestlings of other birds, but we don’t know how common this is. In an extensive study of Blue Jay feeding habits, only 1% of jays had evidence of eggs or birds in their stomachs. Most of their diet was composed of insects and nuts.

Have a great week!
Steem on,
Mike