It looks like he fell 1-2% short of an absolute majority:

Democrat Jon Ossoff is headed for a runoff in June against a Republican contender after failing Tuesday to score an upset victory to represent a suburban Atlanta district in Congress.

CNN called the race just after midnight.

The 30-year-old investigative filmmaker aimed for an outright win in the 6th District race, but a furious Republican counterattack joined by President Donald Trump appears to have kept him under 50 percent.

I would give him no more than a 1 in 4 chance of winning the runoff.