The northbound mainlanes reopened at 7 a.m., nearly five hours after the fatal crash.
Houston police said an off-duty lieutenant, who they believe was on his way home, hit and killed a person crossing the freeway around 2:25 a.m.
Investigators said they don't know why the pedestrian was trying to cross the freeway when they were hit and killed.
The off-duty lieutenant was driving an unmarked city vehicle during the crash, HPD said. After the initial impact, an SUV hit the lieutenant's car.
Police said the two people inside the SUV and the lieutenant were not hurt.
"It is going to be an ongoing investigation that will last several hours," Asst. Chief Adrian Rodriguez said. "We are still waiting on several investigators to arrive at the scene and it will take time to process the scene."
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The lieutenant will be placed on administrative leave as the investigation into what exactly led up to the crash continues.
So far, police have not revealed the age, gender, or identity of the person who was killed. The lieutenant is around 44 years old and has 14 years of service, according to HPD.
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