The FBI knew about him.
And it would seem to be a “no-brainer” for the vetting process to have noticed his name actually translates into “Sword of Allah”. The psychopath followed the teachings of his Koran and waged murderous jihad on innocent men women and children. Mowing them down as they peacefully rode their bicycles, with a rented truck in a pre planned Islamic attack.
Listen to report with Matt Bracken at the 6:00 point in the video