Apparently there are two kanimas creepin in Beacon Hills, which means the kanima who has killed people has not to be Jackson.
The two kanimas can be told apart by the color of their scales. Kanima!Jackson has blue scales while the other kanima has more greenish ones and looks older than kanima!Jackson.
I predict that the other kanima is Jackson’s birth father or mother and also the person in the car.
I’d guess Jackson goes through this change now because one of his parents is close and has triggered his kanima side.
Edit: My love Naya just made me aware that Jeff has stated that it was triggered by the Alpha bite. I still guess a parent is in town because maybe he or she has felt something and we know that Jackson has to deal with one of his birth parents, I think it’s the father, in this season.
For those who asked where I got the info from: teenwolf.wikia.com