Um you should have stayed 45 minutes on stand. I have a few coyotes show up at the 35 to 45 minute mark...
Since they were howling prior to your calling probably a coyote. Did you call constantly or did you do long gaps of silence in between your calling? If you remained silent for long periods of times it was probably a coyote
..Hearing actual live coyotes howling, coyotes are there, minimal calling and do the silent thing..They will come in for a looks see then...
What kind of light lens(red)? were you using and what color were the eyes?
If the eyes were going up and down could be a predator running and trying to get in line...Once in line with you and the wind was blowing toward it it's always over when it comes to Eastern coyotes....
If the eyes were going side to side.. I don't know what it could be?

??/