Multiple orders received without the account holder's knowledge/permission

When I logged into my account this morning I noticed I’d received a large number or orders, placed between 2am and 4am. This arose suspicion as it’s very unusual for me to receive any orders at that time of the morning. My first thought was that another seller, who has been harassing me over the past few weeks, including a threat to kill me this morning, had set up a bunch of new buyer accounts in order to place orders, leave negative feedback and open A-Z claims in an attempt to damage my account. I got in contact with seller support who assured me that all the orders came from genuine accounts that had previous order history.

Despite this, I was still suspicious, so I managed to get in contact with some of those customers. So far, every one of those people has told me that they did not place an order. I have then received cancellation request messages from those people via Amazon, which suggests that not only did these people not place an order, but the order was placed using their genuine account. So somebody has managed to place multiple orders through already existing accounts connected to genuine people.

How is this possible?

My suspicion is that the seller I mentioned has found a way to place these orders. Perhaps they have received orders from these Amazon account holders, which has given them access to these accounts somehow.

I have already reported the issue of harassment, which is easy to prove as it’s in my buyer-seller messages, but proving that the seller may have hacked these accounts will be more difficult.

Or I could be barking up the wrong tree entirely. This could be a glitch.

Either way, it’s very worrying