He was an abortion provider (I will not insult doctors by calling Gosnell a doctor) that was providing illegal late term abortions, and even killing babies that managed to survive his tactics and be born alive. An absolute ghoul.
He was convicted for murder once these actions were revealed by a citizen journalist in 2014, and has been serving three life sentences.
It isn't too surprising you haven't heard of this. National media absolutely buried the story, and only after Internet outlets like Drudge were putting it front and center did the national news -briefly, begrudgingly- cover it.