Without much doubt, I suspect Mcallister because of the following points:

1. He is around 6 feet tall. 
2. He has rough hands 
3. He is not muscular or soft
4. He has short straight hair.
5. He is very calm in the roughest of times. Look at the next episode, even Brett Stiles got scared when Jane pointed a gun at him but Sheriff looked unmoved.
6. In the room with Bertram and Smith, look closely after Jane leaves, how Sheriff is staring at Bertram. He is the only one in the room who sounds a bit shocked when Jane talks about Sophie Miller. Jane cannot spot he is faking it as he is a pathological liar.
7. He wears the same shoes as RJ.
8. He said he likes to hunt anything with a face. That makes sense.
9. In season 6 episode 3, at the end look at him shooting the suspect, bull's eye. RJ too had shot accurately in season 2 finale
10. He shot with his right hand in the season 6 episode 3, while he uses his left hand to pull up Jane and to use his walkie talkie. Well apart from him, RJ is the only one who can use both hands easily.
11. None of the other suspects have been shown to be smarter than PJ except Stiles. But if you watch the episode 3 of season 2, you can clearly say that Sheriff is a lot smarter. Even Jane was surprised when he climbed the ladder. He said "where did you come from?" Only RJ has been able to outwit Jane till now. Maybe Sheriff got to know when they visited Napa that they had come to investigate him. Thats why he kept a close watch on Jane.
12. His age according to the script will be around 50 by now. So the Kid at that farm would be around 21 years old. Fits it.
13. The kid portraying Sheriff looks very much like him. Its got to be him.