Jakeem Grant ran the fastest 40-yard dash in history, but there are some who doubt it really happened. He has a message for those people.

Grant took to Twitter Friday following his blazing showing at Texas Tech's Pro Day to address skeptics (and haters) who doubted his speed. You can see his humorous message to those people below.

To put Grant's 40-yard dash into perspective: Bo Jackson and Deion Sanders, two of the fastest NFL players ever, recorded a 4.13 and 4.19, respectively.

While Texas Tech Athletics officially recorded Grant's 40-yard dash at 4.34 (still insanely fast), others at the event backed up the wide receiver's claim.

NFL Agent Erik Burkhardt, who previously represented Johnny Manziel, vouched for Grant's 4.1 dash on Twitter.

And 24/7 Sports insider Luke Rodgers said that a New Orleans Saints scout recorded Grant at 4.1.

It's not completely clear why Texas Tech Athletics is signing off on the 4.34 time and not the 4.1, but it's easy to speculate.

Regardless, one thing's for sure: Jakeem Grant is damn fast.

See some of Jakeem Grant's highlights with Texas Tech below