This is a gopher snake's best imitation of a rattle snake.
And another tough gopher snake:
Unless you are a rodent or other prey item, snakes will not chase you. Even the most venomous and feared snakes in North America will not pursue people and are sometimes hard to photograph because they quickly flee when approached. I have witnessed water moccasins swim up to investigate when people are splashing in the water, but they swim off after seeing people. The closest I have come to being pursued by a snake has been the result of gopher snake encounters. When an adult gopher snake assumes a hissing/defensive posture, it will sometimes pursue for several feet in an attempt to scare someone that isn't heeding its warning. This has never been more than a few feet and is always the result of me intentionally getting too close to a defensive snake.