Earlier in the day, the office of the Istanbul mayor said that unknown gunmen had opened fire at the Istanbul chapter of Turkiye's opposition conservative Good Party. Police found bullet holes in the building and the adjacent office block.
"It was not an assault. A security guard of a nearby construction site tried to prevent an attempted robbery and fired shots. Criminals ran away toward the building of the Good Party, with the bullets accidentally hitting the cafe in the party's building," the police department said in a statement, the NTV broadcaster reported.
The gunman was detained since he had no license for the gun, the police added.
The police's findings run counter to the statement by Good Party leader Meral Aksener, who laid the blame for the shooting on Turkish President Recep Tayyip Erdogan, telling him on social media to take back "the bullets that come at us."
Turkish Interior Minister Sueleyman Soylu urged people to "be careful with accusations" and trust the government and police.
The Good Party is part of the National Alliance, an opposition six-party electoral alliance, that declared the leader of the Republican People's Party, Kemal Kilicdaroglu, as the alliance's single candidate for Turkiye's upcoming presidential election scheduled to take place on May 14.