Police tasings, which have provided endless entertainment over the last few years, are commonplace for itchy triggerfingered cops. According to SFGate, that's just what Bart cop Johannes Mehserle wanted to do in lieu fatally shooting and killing Oscar Grant on New Year's Day.
In court today, Attorney Michael Rains "wrote in a court document that a second BART officer, Tony Pirone, reported hearing Mehserle say just before shooting Oscar Grant, 'I'm going to tase him, I'm going to tase him.'" Did Mehserle mistake his pistol for his taser? We can't say just yet, but this sounds like it could be Mehserle defense.
The Gate goes on to say that Mehserle was described as 'looking stunned after he shot Grant ... [and that 'had an expression on his face like, 'Holy s-, what happened or what did I do, with his hands around his head.'" (At least so say the defense attorney.) Which is to say, it's a safe bet that Mehserle did not intend to kill Grant and that he felt remorse after doing so, hence a tragedy for everyone involved.
Conspiracy theorists, feel free to vent in the comments.