Why did my dog just snap at my husband?

My husband and I have a 2.5 yr old Engligh Springer Spaniel named Tracker he is EXTREMELY attached to me. We have never has any occurances with snarling or anything unless he gets something he's not supposed to have...(dryer sheet, sock, etc) Tonight was like any other night, I went to bed around 10 and was OUT when I awoke to my husband saying "Tracker it's me, stop. Tracker, stop growling, it's just me buddy" My husband then turned on the light, by which time i was completely awake, and Tracker was right next to me, head down, deep growl. My husband said, "Come on bud, time to get off the bed" same as EVERY night of the week, and Tracker lunged at him. I jumped out of bed in panic, as this is completely out of the ordinary. It was like he wasn't himself. We are both so freaked out by how odd this is, that we can't sleep. Now Tracker is very apologetic and just wants to be loved on. My husband is deploying in 2 months and ill be moving home with our dogs...i worry about this kind of behavior around my young niece and nephew. Any advice?