Mamadou Diallo beat Alex Nash, a 43-year-old career criminal, after finding him shirtless in the hallway. Diallo had rushed home after getting a call that a guy was trying to rape his wife.
Diallo, 61, had a tire iron and beat Nash to death with it.
Diallo was then charged with manslaughter, because he committed the beating as Nash was leaving, not as he was raping (lol).
The public considered Diallo a hero, and the New York DA's office seems to be acting accordingly. They downgraded his manslaughter charge to assault and possession of a deadly weapon, and released him without bail.
He is still expected to be charged, though. It is possible that the DA will purposely put out a non-effort with the prosecution for appearance sake, thus effectively letting him off.
Something similar occurred in 2012 when a former childhood victim of a serial child molester tracked the 65-year-old former priest down to a rest home, and beat him. Knowing that the priest had indeed committed horrible acts of molestation against the perpetrator as a young boy (for which he was never charged), the prosecution seemingly intentionally put forth a weak case against him, and the guy walked free.