The wreck happened just before 4pm on Highway 59 northbound before the Parker exit.
The name of the child killed has not been released but police say it's a boy around five years old. The remaining four victims were taken to the medical center. Investigators say at least one was critical on arrival.
Eyewitnesses say it happened quickly.
"I heard this loud pop like a gunshot and the next thing I know, I got my eyes set on this SUV; it started sliding sideways and once it did that, it hit that wall and it started rolling over. All I did was stop assist them," an eyewitness told us.
Police believe the driver of the SUV lost control after a blowout, striking a concrete barrier in the HOV lane before flipping the vehicle several times. Luggage lay on the freeway near the crash site. Investigators believe the passengers may all be part of a family on vacation together.
"Apparently they were heading maybe back to Oklahoma. They have out-of-state plates, but we aren't too sure right now," HPD officer Andrew Valencia said.
A young boy was pronounced dead at the scene. Four more victims were taken to the hospital.
Just a few cars at a time could pass through as investigators worked through rush hour to clear the scene. For those who were there first, they did all they could to help.
"There was nobody else involved. All we did was there were five or six and we assisted them until the EMT got here, calm them down you know," an eyewitness said.
Police say no charges have been filed in the accident at this time.
The accident shut down most of the northbound lanes of Highway 59 for several hours, causing a major traffic backup.