Droid, yes. Murderers are not excluded from Teshuva as far as I recall. I am sure it won’t come easy but possible? Yes. Kayin comes to mind. Nevuzeradan even more so. He killed over 14,000 innocent people – then did Tshuva (I’m sure it was no easy ride) and became a Ger Tzedek. (Sanhedrin 96b).
Again don’t get me wrong. The enormity and depravity of what Aron did is not in any way lessened. A murderer is a murderer and without Tshuva he is the worst of the worst. It still is just a huge unfathomable kindness of Hashem that no matter how low, how wicked, how depraved a person has become – He is still our Father and with the necessary true effort anybody can return. This is stated many times in Chazal, Rambam, Sharei Tshuva of Rabenu Yonah and countless other seforim. What Tikunim are necessary I don’t know – but a lost case? Chas Veshalom. L’val yidach mimenu nidach.