Who Trades Atico Mining?

I very often wonder who invests in stocks. Let me take an example of Atico Mining, a small copper producer, operating the El Roble mine in Peru.

On August 15 the company released the following info:

VANCOUVER, BRITISH COLUMBIA--(Marketwired - Aug. 15, 2017) - Atico Mining Corporation (the "Company" or "Atico") (TSX VENTURE:ATY) reports a temporary work stoppage at the El Roble mine pending final inspection of the clean water discharge system. The Company will work with provincial authorities to confirm the integrity and safety of the system as quickly as possible, beginning tomorrow August 16, 2017.

Here is the reaction of the market:

 

source: stockcharts.com

Notice that in middle June 2017 Atico shares started an impressive move up - between June 16 and August 14 these shares gained 53.4%.

However, on August 15, since the beginning of the trading day, somebody was desperately selling Atico shares, which resulted in a final drop of 6.7% (blue arrow). It looks like somebody knew about the company's problems.

Then, the next day, when the info was known to everybody, the shares tumbled 13.3% at their selling climax (red arrow).

Summarizing - in just four after this "disastrous" news a decent company lost 14.6% in value.  

Today the company released this info:

VANCOUVER, BRITISH COLUMBIA--(Marketwired - Aug. 21, 2017) - Atico Mining Corporation (the "Company" or "Atico") (TSX VENTURE:ATY)(OTC PINK:ATCMF) is pleased to report that further to the news release announced August 15, 2017, the final inspection by provincial authorities concluded successfully and the operations at El Roble mine have resumed as of August 18, 2017.

So now everything is back to normal. However, a question remains open: who is trading stocks? Who thinks that a minor technical issue, a usual thing in the mining industry, can derail a decent company in just two days?

UPDATE:
Today Atico shares are up 10.5%. My question is still intact - who trades these shares?