Why didn't Stephanie. . .Possible Spoilers

Some of the characters' actions in the movie were driving me crazy. For example, when Stephanie is looking for Ellie, why would she chase the kidnapper into the jungle and follow him under the bridge? Was she looking to be kidnapped too? And when Stephanie finds Ellie and is helping her escape, why doesn't Stephanie take a 2x4 or rock to knock the kidnapper out? She's surrounded by them! Ellie does it once they're outside, but not enough. I would have kept beating the guy until he was unconscious, not just groaning on the floor. And finally, why didn't Michael shoot the kidnapper to show the cop he wasn't playing games, instead he just decides to trade Stephanie for his missing girlfriend and turns his back on the cop. Yes, I know it's a thriller, but do the characters have to make so many dumb moves?