The slain victim was a man shot in the head inside his vehicle, acting Houston Police Chief Martha Montalvo told reporters. A suspect also was killed, police said.
A second armed man was injured and taken into police custody. Police originally described him as a suspect, but later said they weren't sure.
"He's telling us a version as to what his involvement is," Houston Police spokesman John Cannon said. "We need to verify that before we say anything publicly."
A motive for the shooting wasn't immediately clear.
"We do not know what started this," Montalvo said, "but what we do know is they were shooting randomly, just at whoever."
A total of eight people were shot, including the suspect, police said.
Two deputies were injured in the shooting. One was treated and released after his vest saved him; the other was shot in the hand, Montalvo said. Three other victims were hospitalized with non-life-threatening injuries.
Police: Gunman had two weapons
Cannon said the main suspect in the shooting wielded at least two weapons: a pistol and an AR-15 rifle.
According to police, the suspected gunman used the pistol to shoot dead a man in his 50s who was parked at an auto detail shop.
"(The victim) had simply driven there, parked his car to get detailed, and within a minute or two, that's when the suspect came out and shot him for no apparent reason," Cannon said.
Several people in the area said their vehicles were shot at, CNN affiliate
Police posted a photo on Facebook showing a patrol vehicle's windshield riddled with bullets, saying the officer inside was "lucky to be alive."
Videos posted on social media showed police cars racing through the neighborhood as gunshots rang out and a plume of smoke rose overhead.
Suspect fired at police chopper
As a SWAT team and a police helicopter responded to the scene, at least one gunman opened fire at the chopper, police said. The aircraft was hit by at least five bullets, Montalvo said.
Authorities haven't released further details about the victims or the suspects.
A fire also broke out at a nearby gas station during the shooting. Investigators believe it may have been caused by gunfire hitting a gas pump, Montalvo said.
The shooting left people in west Houston rattled, CNN affiliates reported.
"You don't expect to hear gunfire on a Sunday morning in this neighborhood," resident Bill Robinson
. "So, pretty quickly you put two and two together and say, 'it is gunfire,' and get your family safe and get locked down."
Ryan Harper told KTRK that he watched out a bedroom window while his wife and kids huddled in a closet.
"We saw the cops and the SWAT run down one of these driveways in the backyard," he said.
Montalvo, the acting police chief, said shootings can happen in any neighborhood.
"It doesn't really matter where you live," she said. "But the police were here. They responded very very quickly at their own peril."