This guy may have done photography, but it doesn't mean he's a professional photographer.

Shutter speed is one of basics a pro photographer would worry about. You need to understand a few other things that affect shutter speed to see if the shutter speed is

Another basic is f-stop. This indicates how open or closed the aperture of the camera is.

See here https://upload.wikimedia.org/wikipedia/commons/thumb/8/87/Aperture_diagram.svg/1280px-Aperture_diagram.svg.png

This affects the look of the picture. It affects what is in focus and how deep the field of focus. You usually set the f-stop first and from there you determine the shutter speed. And both of these are affected by the focal length

If your lens is wide open, you're letting in a lot of light, so to compensate you want the shutter to be really fast. Otherwise the image is overexposed.

He posted the EXIF data he used 24 mm lens. Wide angle good for up close shots. 1.6 f-stop WIDE open lots of light let in 1/8000 sec shutter speed. Super fast less light let in

This combo makes sense if he was super close on a sunny day. He was like 3-4 feet from Trump.

But how did e capture the bullet streak?

That's still luck. He was probably shooting in burst mode. That camera can take 30 images a second. That burst of 30 images if it started slightly differently might have not captured the bullet because the lens might have been closed in that instant.