I don't think a stray Avada or an accident or Ebola or whatever would have killed Harry while he still had that eighth piece of Voldemort's soul inside of him. I realize this is different to your question, which asks specifically if Harry had been killed, but I don't think Harry could have been killed by any means while Voldemort was still alive.
As long as Voldemort himself was alive, Harry could not die, because Voldemort tethered Harry's life to his own when he used Harry's blood (specifically) in the resurrection potion in Goblet of Fire. The protective enchantments that flowed through Harry's blood, via Lily's sacrifice, now flowed within Voldemort's veins, creating a reciprocal, symbiotic connection between Harry and Voldemort. From Deathly Hallows:
‘But if Voldemort used the Killing Curse,’ Harry started again, ‘and nobody died for me this time – how can I be alive?’
‘I think you know,’ said Dumbledore. ‘Think back. Remember what he did, in his ignorance, in his greed and his cruelty.’
‘He took my blood,’ said Harry.
‘Precisely!’ said Dumbledore. ‘He took your blood and rebuilt his living body with it! Your blood in his veins, Harry, Lily’s protection inside both of you! He tethered you to life while he lives!’
‘I live ... while he lives? But I thought ... I thought it was the other way round! I thought we both had to die? Or is it the same thing?
‘He took your blood believing it would strengthen him. He took into his body a tiny part of the enchantment your mother laid upon you when she died for you. His body keeps her sacrifice alive, and while that enchantment survives, so do you and so does Voldemort’s one last hope for himself.’
‘What you must understand, Harry, is that you and Lord Voldemort have journeyed together into realms of magic hitherto unknown and untested. But here is what I think happened, and it is unprecedented, and no wandmaker could, I think, ever have predicted it or explained it to Voldemort.
‘Without meaning to, as you now know, Lord Voldemort doubled the bond between you when he returned to a human form. A part of his soul was still attached to yours, and, thinking
to strengthen himself, he took a part of your mother’s sacrifice into himself. If he could only have understood the precise and terrible power of that sacrifice, he would not, perhaps, have dared to touch your blood ... but then, if he had been able to understand, he could not be Lord Voldemort, and might never have murdered at all.'
Deathly Hallows - Pages 567-569 - British Hardcover
It would be only after both the eighth piece of Voldemort's soul was destroyed and Voldemort himself was dead that Harry would become mortal and vulnerable to death once again. Does this explain how Harry could manage to live through, say, being decapitated, or having a twelve-ton portion of the Hogwarts castle fall on top of him while Voldemort was still alive? No. But this is what canon says regarding Harry's mortality and susceptibility to death in general. The eighth portion of Voldemort's soul inside of Harry must be destroyed by Voldemort himself, so I believe the answer to your question is no.
‘So the boy ... the boy must die?’ asked Snape, quite calmly.
‘And Voldemort himself must do it, Severus. That is essential.’
Another long silence. Then Snape said, ‘I thought ... all these years ... that we were protecting him for her. For Lily.’
‘We have protected him because it has been essential to teach him, to raise him, to let him try his strength,’ said Dumbledore, his eyes still tight shut. ‘Meanwhile, the connection between them grows ever stronger, a parasitic growth: sometimes I have thought
he suspects it himself. If I know him, he will have arranged matters so that when he does set out to meet his death, it will, truly, mean the end of Voldemort.’
Deathly Hallows - Page 551 - British Hardcover