It began in the 4000 block of Belle Park Drive with a traffic stop, according to Houston police.
The armed passenger held the pickup's driver at gunpoint for more than two hours, police said.
A woman on the scene, who identified herself as Carmen, said she's related to the driver. She believes the passenger who was holding her cousin at gunpoint was his friend.
"The man asked him to take him somewhere, and then he stopped and pulled a gun on him," Carmen said. "It's a friend of his."
It wasn't clear what charges the gunman faces.
The driver was arrested on a warrant for assaulting a family member, police said.