At least 45 people were injured in the explosion between two underground stations on Monday afternoon.
Baratov wrote he was suspended from high school for "threatening to kill my ex-friend as a joke.
The suspect was found in a truck in a parking garage, said Capt.
Police believe Jaber al-Bakr, also a Syrian, was planning a bomb attack and had links to so-called Islamic State.
Thai police arrested four people suspected of preparing and organizing the attacks.
French police have identified the second terrorist who attacked the church in Normandy as 19-year-old Abdel Malik Petitjean.
Two weeks prior to the Olympics, Brazilian authorities announced the arrest of 10 people.
The aftermath was captured on amateur video.
The main suspect in the terrorist attacks in Paris Salah Abdeslam was handed over to the French authorities.