Omar Mateen Born to Two Afghan Citizens Automatically a US Citizen

I haven't seen this mentioned ANYWHERE. Omar Mateen, the shooter responsible for the worst mass murder on American soil, was born in New York City in 1986. Both of his parents are Afghan citizens. I cannot find if they are going through naturalization, I'm almost certain NO as the father of Omar is running for President of Afghanistan. Two NON CITIZENS were allowed to produce a citizen?

Omar Mateen should not be a citizen. Omar Mateen should not have been a registered voter. Omar Mateen should not have been able to purchase the guns he bought just before the murders.