Mine free range from about noon to 6-7 P.M.; then I put them in their run and close the gate an hour or two before it's supposed to get dark. Just before dark, they all go into the coop and get on the roost; after they're on the roost, I go out and close up the pop doors. I suppose anything's possible, but it isn't likely that a predator will ever get into my run to kill a chickens.
https://www.backyardchickens.com/web/viewblog.php?id=9574
The only reason that I go out at night to close the pop door is because we don't let them out of the coop until about 10 A.M.; that way the rooster does not wake up any neighbors. They're so used to it that they stay up on the roost until 10 A.M., and meanwhile the rooster pretty much keeps quiet. He sure makes a ruckus to be let out of the run though.
https://www.backyardchickens.com/web/viewblog.php?id=9574
The only reason that I go out at night to close the pop door is because we don't let them out of the coop until about 10 A.M.; that way the rooster does not wake up any neighbors. They're so used to it that they stay up on the roost until 10 A.M., and meanwhile the rooster pretty much keeps quiet. He sure makes a ruckus to be let out of the run though.