Police arrested 25-year-old Oktai Enimehmedov, a Bulgarian man and ethnic Turk from the Black Sea town of Burgas. Enimehmedov was also carrying two knives, officials said.
It was unclear how he got past security and into the meeting hall. His motive was not known.
Bulgarian officials say Enimehmedov has a criminal record for drug possession, robberies and hooliganism.
Saturday’s incident was the most serious attack on a politician in post-communist Bulgaria since ex-prime Minister Andrei Lukanov was shot dead near his home in 1996.