He is an atheist because he does not believe in any one of the available gods such as Jesus, Yaweh, Mohammed or Zeus.
Presumably he does not believe in any of these things because he has realised that:
Buddhism.
Theistic means believing in a god or gods, in a divine existence. Atheistic is denying, not accepting the existence of anything like that.
There is none!
atheistic
Most Czech's are atheistic. It is the most atheistic country in the world, with over 60% of the population declaring no religious affiliation.
Communism is atheistic.
That life exists.
His religious views are not known.
Atheistic evolutionary humanism.
He was totally cool with it.
No! They are Christians.
Atheists believe friends exist.