I just saw I am Legend and I was wondering about the scene where Will Smith gets caught in a sling/ trap??Help

I just saw I am Legend and I have one question? The part where he is driving and sees the dummie "Fred" standing in the street. He walks up to it and yells at it and is confused because he knows he didnt put it there? Who put it there and set a trap? Was it Will Smith and he just started to loose it and forgot that he set it? Or was it the infected after watching Will Smith catch one of there own the same way? please help, Thanks

The zombies set that trap with "Fred" as bait in retaliation to the trap he set earlier in the movie that killed that one zombie who came flying out with a black sheet over it.

I saw it too and I think that it was the infected that put it there. He yells at it because after three years alone, you start to get a little crazy.

2 possible answers:

1: The zombies put it there to trick Neville.
2: Neville set it up to catch a zombie, and FORGOT it was there. He did start to lose his mind.

I think Neville put it there and forgot. He was losing his mind.