It's tough to diagnose this. Where do you live?
The fact that the top of the crown is showing these symptoms is interesting. There is no mechanical damage to the stem or possible root damage caused by compaction/disturbance around the soil?
I wonder if this could be oak wilt, which is an invasive disease that is bad news for our native oak species. Red oak is particularly susceptible too, which I believe is your tree?
I'd chop it down and look for discoloration in the cambium and insect bore holes. Depending where you live, you might want to submit samples or let the city know about it (ie oak wilt might not be known in your area yet). Keep us updated.
