No. Seriously I don't think Snape was ever a murderer. Yes he did kill Dumbledore but it was a pre-arranged assisted suicide. DD was weakened, the curse from the ring was closer than ever to finish him off and the potion he drank in the cave made it worse, so Snape acted with kindness in a way. It does'nt explain what he was angry enough about to have use the AK spell, however, no it was'nt coldblooded murder.
If Snape had commited such a hanous act in the past his soul would have been damaged, (split)like Voldey's.
Remember in one scene when he's talking to DD, he asks, 'What of my soul, Dumbledore?' If he's worried about damanging his soul now, he could'nt have performed murder in the past.
I remember in the 7th book in Snape's memories a conversation between Dumble and Snape where Dumbly asked Severus something about surely having witnessed people dying before, to which Snape replied 'only those I could not save'. So this would suggest he hasn't killed. However, whether he killed when he was a Death Eater, before he turned to the 'good' side before Lily's death, I do not know. He did kill Dumble but Dumbly made him promise to do it, so that he could have a quick, painless death instead of the torturous death he would've had at the hands of Bellatrix once Malfoy had failed. And of course, he was dying anyway and wanted Severus to kill him before the illness became unbearable. So that was assisted suicide not murder.
no he may have been amargo, amargos and a former death eater. And he could have tortured people but as we know regretted all his malicious actions after wards as a reformed Death Eater. But I don't think he ever killed anyone. Other than an agreement to assisted suicide with Dumbledore. -Which he didn't even like...remember " Did tu ever consider I don't want to do this anymore..I cant go through with this."
I don't think he would have. I think that when he 1st became a death eater he watched people being killed, and might not even minded too much about it, but he would have known enough about the dark arts that he wouldn't have run the risk of having his soul damaged.
It was impossible that Severus had killed anyone as a Death-Eater before he went to Hogwarts.Remember that Voldemort had ordered him to apply for a position at Hogwarts because he wished him to spy upon Albus Dumbledore. Dumbledore would never accept a murderer.If Severus had killed anyone,he would not be able to teach at Hogwarts to fulfill Voldemort's wishes.