21.07.2026 15:11
In the Gülistan Doku investigation, former police officer Gökhan Ertok, who is detained, stated in his testimony as a witness that Mehmet Aca, the owner of ACA Bilişim company, introduced him to the then Tunceli Governor Tuncay Sonel, and that Aca told his employees, 'Do all the governor's work.' He recounted that Sonel asked him to examine Doku's SIM card, and upon that, he called Aca, who replied, 'I have knowledge, do what is necessary.'
In the investigation into the disappearance of university student Gülistan Doku in Tunceli on January 5, 2020, remarkable statements have emerged regarding the role of Mehmet Aca, the owner of ACA Bilişim company.
Former police officer Gökhan Ertok, who was heard as a witness at the Erzurum Chief Public Prosecutor's Office, named Mehmet Aca in the process of examining Gülistan Doku's spare SIM card, accessing the young woman's social media accounts, and fulfilling requests from the then Tunceli Governor Tuncay Sonel.
According to Ertok's testimony, Mehmet Aca was the person who introduced him to Tuncay Sonel, directed IT tasks from the governor's office to his employees, and was previously aware of the examination of Gülistan Doku's SIM card.
"I WAS INTRODUCED TO TUNCAY SONEL BY MEHMET ACA"
Gökhan Ertok explained that his relationship with Tuncay Sonel began through Mehmet Aca. When asked under what capacity he fulfilled Sonel's requests to identify and shut down social media accounts, Ertok directly pointed to Aca.
The witness stated the following claim in his testimony: "I was introduced to Tuncay Sonel by Mehmet Aca. He told me, 'Do all the governor's work.' After all, I was working at his workplace. That's why I fulfilled Tuncay Sonel's requests."
According to this account, Mehmet Aca was the person who connected Tuncay Sonel with ACA Bilişim employees and demanded that requests from the governor's office be fulfilled.
FOR THE SIM CARD, HE SAID "I HAVE KNOWLEDGE, DO WHAT IS NEEDED"
Gökhan Ertok stated that he learned about Gülistan Doku's spare SIM card being sent to Ankara first from Şükrü Eroğlu, then from Tuncay Sonel. According to Ertok's statement, Sonel asked him to examine the SIM card and obtain information that would help find the young woman.
Ertok said that immediately after this conversation, he called his boss Mehmet Aca and relayed Sonel's words. Ertok recounted Aca's response with these words: "I told Mehmet Aca on the phone. He told me, 'I have knowledge, you do what is needed.'"
This statement raised the suspicion that Mehmet Aca was aware of the process before the spare SIM card was examined by Ertok and that he authorized the employee to proceed.
SIM CARD WAS TAKEN TO ACA BİLİŞİM OFFICE
Gökhan Ertok stated that he received the spare SIM card belonging to Gülistan Doku, sent to Ankara by bus, from AŞTİ. He said he then took the card to ACA Bilişim's home office in Ankara Etimesgut, owned by Mehmet Aca.
Ertok admitted that he first inserted the spare SIM card into an old Samsung phone belonging to his mother and accessed Gülistan Doku's WhatsApp and Instagram accounts through this card.
The witness stated that he might have also used the company's computers during the operations, saying, "I might have accessed Gülistan Doku's accounts from the computers at the workplace owned by Mehmet Aca."
With this statement, whether the technical infrastructure of ACA Bilişim was used to access Doku's digital accounts became one of the key topics of the investigation.
GÜLİSTAN DOKU'S ACCOUNT WAS ADDED TO COMPANY PANEL
Ertok also said that he added Gülistan Doku's Instagram account to a system called "SMM Panel" used at ACA Bilişim. It was stated that this panel was used to upload followers and likes to social media accounts, track login and logout activities, and receive notifications about accounts.
Ertok explained that because he added Gülistan Doku's Instagram account to this panel, login and logout activities on the account could be sent as notifications to the company computer or his email address.
This statement by the witness raised the question of under what legal authority a missing person's social media account was added to a private company's system.
THE COMPANY COULD CLOSE ACCOUNTS
Gökhan Ertok also stated that at ACA Bilişim, not only were followers or likes uploaded to social media accounts, but user accounts could also be disabled through mass complaints.
Ertok stated that through the panel systems at the company, up to 10 million followers or likes could be directed to an Instagram account, and target accounts could be rendered non-functional by creating numerous complaints using bot accounts.
Ertok said that he had the social media account named "Kerbela62," which criticized Tuncay Sonel, closed by having it reported by 50-60 people simultaneously. According to the witness, most of the work came from Mehmet Aca's circle. Employees did not find customers on their own but carried out transactions directed by Aca.
A THREE-PERSON ADVANCED IT TEAM
Ertok stated that during the period Gülistan Doku disappeared, two other people besides himself, named Sefa Karasu and Emre Ezertaş, were working at ACA Bilişim. Noting that all three employees had advanced knowledge in software and IT, Ertok stated that Mehmet Aca did not visit the office often, mostly directing work remotely.
The witness said he saw Aca only 3-4 times at the office during his approximately one-year working period. He explained that payments for the work done were generally sent to the company account, and Aca paid the employees' wages from this account.
WERE THEY ALSO PAID?
Ertok's testimony also included that money transfers were made in return for the social media activities allegedly carried out at the request of Tuncay Sonel. Ertok first said he did not receive any financial benefit from these transactions. However, when reminded of the total 10,000 lira transfers in MASAK records, he admitted to receiving the money and distributing it to other company employees.
The witness stated that the 20,000 lira sent after another transaction was in return for fulfilling Tuncay Sonel's request. Ertok's statement, "He sent me money because I fulfilled Tuncay Sonel's request," raised the question of whether these payments were related to the work carried out within ACA Bilişim.
"I DON'T KNOW WHO TOLD ABOUT THE SIM CARD INCIDENT"
Gökhan Ertok argued that Mehmet Aca was aware that the spare SIM card belonging to Gülistan Doku would be examined, but he said he did not know who gave this information to Aca.
Ertok said, "I don't know who, when, and how told Mehmet Aca about this SIM card incident." This account brought up the question of whether Aca had prior direct contact with Tuncay Sonel, Şükrü Eroğlu, or other individuals.
It was stated that separate investigation findings regarding Mehmet Aca's financial transactions with Tuncay Sonel were also being examined in the case file.
CONNECTION WITH HOSPITAL RECORDS BEING INVESTIGATED
Witness Gökhan Ertok was also asked whether Mehmet Aca had other companies offering hospital information management system services to healthcare institutions or employees familiar with these systems.
Ertok stated that he does not know whether Aca has a company providing HBYS services to hospitals.
Ertok, who claimed that he was not involved in the deletion of some records at Tunceli State Hospital, argued that no such request was made to him or the company he works for.
According to the witness statement in the file, Mehmet Aca introduced Gökhan Ertok to Tuncay Sonel; he instructed his employees to carry out the tasks coming from Sonel, and he knew in advance that Gülistan Doku’s spare SIM card would be examined.
Again, according to the statements, when Ertok informed him about the SIM card procedures, Mehmet Aca said, “Do what is necessary”; he was the owner and manager of ACA Informatics, where the operations were carried out; he had the technical infrastructure and employees that could intervene in social media accounts.
To what extent Mehmet Aca directly participated in the operations, what instructions he gave, and how aware he was of the interventions made to Gülistan Doku’s digital data will emerge as a result of the investigation.