& who killed Ian mainly

Alison was the one that pushed him off the bell tower and when we next saw him he looked dead af but he disappeared and reappeared later dead in a barn. Though Alison says she didn't kill him, we never had concrete proof that he was alive between the bell tower and the barn they found him in, since every bit of contact he made was digital and could've been easily faked (texts, etc) so even though it's supposed to be a suicide I think Alison's push killed him and she just covered it up later by moving his body to this barn and staging it to make it look like a suicide.