Investigation into the U.S. Embassy drive-by shooting, which occurred on Aug. 20, in the Turkish capital has been completed on Thursday, according to a judicial source.

The indictment prepared by Ankara public prosecutor Murat Ozcan has designated Ahmet Celikten and Osman Gundas -- who allegedly carried out the attack -- and Gundas’ boss Ersin Bayram as well as Talip Bora Kilic -- the owner of the vehicle that was presumably used during the attack -- as suspects.

The indictment was sent to the 32nd Heavy Penal Court in Ankara.

According to the investigations, the suspects, Gundas and Bayram, allegedly communicated with the Fetullah Terrorist Organization (FETO) with cell phone.

The anti-terror branch of Ankara’s Security Directorate said Gundas had apparently shared videos of Fetullah Gulen, the ringleader of the terror group behind the July 15, 2016 defeated coup.

Bayram also allegedly downloaded smartphone applications linked to the terrorist organization.

According to the Ankara Governor's Office, Celikten and Gundas confessed their involvement in the attack.

Footage from city surveillance cameras shows that Celikten and Gundas scouted the area outside the embassy building 20 minutes before the attack.

The suspects face up to 55 years in prison.

FETO and its U.S.-based leader Fetullah Gulen orchestrated the defeated coup on July 15, 2016, which left 251 people martyred and nearly 2,200 injured.

Ankara also accuses FETO of being behind a long-running campaign to overthrow the state through the infiltration of Turkish institutions, particularly the military, police, and judiciary.