Witnesses have described the moment they heard dozens of shots and saw 'bodies going down' when a gunman opened fire and killed multiple people at an outdoor outlet in suburban Texas.

The shooting happened at the Allen Premium Outlets in Allen, a small suburb north of Dallas and it left at least nine injured and several dead before the gunman was shot dead by police.

 Crowds of people were forced to run and take shelter in stores and some said they saw the killer's body on the ground as they were being evacuated. 

And two people described the shooter as wearing all black and clad in SWAT-like gear. 

Reports from local police sources initially indicated that there may have been two gunmen - the one killed by first-responders and another still at-large - though police are now saying they believe the unidentified gunman in the footage acted alone.

Cops have yet to release a statement confirming any casualties - but in a statement, the town's fire chief said nine citizens were hospitalized, and aerial footage of the scene showed at least four bloodied bodies lying outside of the mall's many stores.