The man behind the wheel of a pickup truck has been identified as 54-year-old Charles Glaze, according to sources.
Sources say Glaze reportedly crossed from the westbound lanes of Highway 99, over the median and into oncoming traffic, striking four vehicles. When speaking to authorities, he reportedly said he didn't know what happened before the crash.
According to sources, Glaze was reportedly wearing an ankle monitor at the time of the crash on Highway 99.
But new details revealed a twist about Glaze. According to sources, he has a criminal history. Glaze was charged in 2017 with aggravated kidnapping and assault out of Montgomery County.
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Investigators say in 2017, a woman was visiting her son's gravesite when Glaze attacked her at the Klein Memorial Cemetery in Tomball.
Deputies say he assaulted her with a Taser and showed her a gun before tying her up with zip ties and a necktie. Deputies say she managed to escape.
In another incident, deputies with the Montgomery County Sheriff's Office say a man matching Glaze's description reportedly made another woman feel uncomfortable at a different Klein cemetery and she reported that to authorities.
Wednesday's crash left twisted metal and shattered glass across all lanes of the Grand Parkway. An off-duty Katy police officer said he was the first to arrive at the scene and helped extract a man from a rolled over Ford F-150.
WATCH: Off-duty officer jumps into action to help after deadly Grand Parkway crash
"The best way I can describe it, mass chaos. A huge field of debris, unfortunately," said Katy Police Officer Johnny Alvarez.
Alvarez saw that Glaze needed help, and because he always kept an extensive medical kit in his personal car, he had exactly what he needed to wrap Glaze's head and treat other people before paramedics arrived.
He said he got on his knees and went through the rear passenger window.
"A lot of people might say it's heroic. In all honesty, I see it as my instinct reaction. Having served in the military, it's the right thing to do. As a law enforcement officer, we took an oath, whether you're on or off duty, in your jurisdiction or not, we always try to preserve life and assist in any shape or form. It's a clock that never turns off," Alvarez said.
The Harris County Sheriff's Office said five people, including Glaze, were taken to the hospital with non-life threatening injuries.
Michael Brown was one of the victims who was killed. He was driving a Chevy.
Deputies said Glaze did not appear to be intoxicated and said he is cooperating with their investigation. Glaze has not been charged in the deadly crash.
The driver apparently has a history of seizures, according to the sheriff's office. It was not immediately known if Glaze was cleared by a doctor to drive.