I think its from family guy because it sounds like something peter would say but it could also be a movie. Goes somethin like this: [it maybe says this] i killed him [then definately says sumtging like this] the i thought, you know what? I shouldnt have done that, didnt think things through, should have rethough these actions
Reminds me of some scenes between DeNiro and Sam Jackson in Jackie Brown, particularly the one after DeNiro's character kills Surfer Girl/Melanie (played by Bridgette Fonda, iirc) in anger, or thinks he did (he's not sure). It went something like: "Where's Melanie?" "Eh...back at the mall, in the parking lot" "What, you left her there" "Nah...I...I shot her" "Whatchu mean you shot her?" "I shot her" "You shot her? Why'd the hell you shoot her for?" "She was mouthin' off, talkin' s***, so I shot her" "Well is she dead?" "Yeah...I think I killed her...I think she's dead" "Well which is it? She's dead or you think she's dead? What if that b**** is still alive, man? I know her! Police gonna come, ask questions, and that b**** is gonna talk, man!" "Yeah...y'know...I know...I'm sorry, I wasn't thinkin', I should've thought that through but, y'know...in the heat of the moment...." That movie, IMHO, is Quentin's best.
