PPC Hacked? Could this be an attack?


Something worrying happened to us today, and I was wondering if anyone has experienced the following:
We noticed that for a Product Sponsored Campaign Ad we were running for one of our products, there was a massive spike in the number of clicks, thus resulting in us being charged a significant amount.
We did not do any bid increasing or any other changes to this campaign in the past 30 days.
Last month, the same ad gathered 103 clicks and had 10 sales, that is in line with a an average 10% conversion rate we have for our product listing.
Yesterday alone, we had 551 clicks (!!!) and the number of sales for the product does not reflect in anyway the huge numbers of clicks we had. We sold 5 units for this particular ASIN, which is what we expect on an average sales day. 95% of the clicks originated from a single keyword from our list.
We have paused the affected ad, and have opened a case with Sponsored Ad Support and asked them to investigate this unusual high number of clicks.

Any thoughts or suggestions are appreciated.

Thank you and best regards

Same buyer? Different people? Ad placed in the wrong place?