How did he get NYPD gear??
Rudy Giuliani probably gave it to him.
Trump was correct in his warning and he will do something about this. I speculate that OMAR is Sunni sect and not Shiite. He is also a Wahhabi. All Wahhabi need to be immediately removed from the general population. All Sunnis need to be reviewed for Wahhabi beliefs. This was a celebration of Ramadan by a Wahhabist.
Bought it on the Internet? Anyone can buy a NYPD grey sweatshirt, I seem to remember them being common when I lived in New York. The other shirt looks like a polo shirt, so again not quite a uniform, but could be made up into an approximation I suppose if one was so inclined.
For instance: Ebay NYPD Shirt listing