According to the L.A Times, the YouTube shooter was an Iraqi refugee.

L.A Times:

Aghdam entered the country as a refugee roughly two decades ago, a family member said. In one of her videos, she said she was born in Urmia, Iran — where she and other members of her Baha’i faith face discrimination — and that her family had spent a year and a half in Turkey.

This has showcased two flaws with the refugee programs that have plagued this country. The first is the inability to vet. This family likely gave off no warning signs yet still brought a terrorist into our country. No proper vetting would have stopped her because she became radicalized as an American. The second is that the children often become more radicalized than their parents. It is clear that her parents were law-abiding citizens but she became radicalized by a leftist organization  PETA.