Family Guy Season 6 episode5

Stewie escapes when Lois recounts what happened after she fell into the ocean. Back at the Griffin's house, he holds his family hostage and points a gun at Brian forcing Brian to drive him to the CIA headquarter after tying up the rest of his family. Having taking control of the world's power grid, he becomes the president of the world.

After Chris sets his family free, they find a secret chamber in Stewie's room. Lois gets fed up with Stewie's tyranny; she arms herself with a knife and some heavy weapons before proceeding to kill her baby.

In a fierce fight, Lois subdues Stewie, but can't kill him. When Stewie is about to kill Lois, Peter arrives, shooting Stewie in the head.
It's then reveals that the whole story is just a simulation. None of them was really happened.