I agree with the posts above. Give him some time to settle in. Is he now in I high traffic area, this could cause stress and him to react this way. Give him a few more days.
Now, I say welcome to the retic world. If the snake was fed in his cage he will always act that way. My retics fire out all the time when I walk by, it makes me pee in my pants everytime but when I get them out of the cage they are fine. They are just very aggressive eaters. Mine still will snap at the hook once in ahwile, but hey that is why you use one. Its not your hand. It will soon figure out the hook is not food and when its touched by that it will calm down. In fact everytime I go to mist my guys, they move up to the front thinking I am food. So I have to open a small crack and start spraying, I gets a snap once in awhile from that, but then calms down. These are the things will you learn as you go.
I use to think I had a mean burm, first night I brought her home she was huffing and puffing everytime I walked in the room, I got tagged twice by her. Both my errors. First time I was acting like a fool with her around my neck singing to my wife the B. Spears song that she sang with the burm and next thing I know it bit my hand. Second time reached in to grab somthing. No hook, and got hit. Stupid mistakes but I learned. She was only 7 ft at the second time and did not wrap with the bite.
Good Luck, you will be fine.
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0.2 Rotts
1.0 Super Tiger
1.0 Amel Retic
0.1 Ball Python
0.1 Red Tail
0.1 Blood Python
1.0 Green Ananconda
1.0 Emerald Tree Boa