“Several people shot by suspect are being transported to area hospitals; unknown exact number or severity of injuries,” the Houston police said on its Twitter account.
The shooter was a Houston-area lawyer, the Texas city’s police chief Martha Montalvo told a news conference. She would not identify the man by name.
Police said they were investigating whether the shooting was motivated by “issues at his firm.”
Of the nine people injured, six were sent to hospitals while three were treated and released near the scene of the incident. One person was in critical condition and another in serious condition, police said.
Police did not disclose what kind of gun was used.
Houston Mayor Sylvester Turner told local television station KTRK that it appeared the motivation for the shooting may have been the lawyer’s relationship with his firm, which “went awry.”
The police chief said there were no indications of any others involved, and that investigators were checking the man’s social media accounts to help in determining his motive.
Police responded to reports of a shooting at 6:29 a.m. local time, and engaged in a shootout with the suspect. “The individual was firing actively at the officers,” Montalvo said.
Houston Fire Department spokesman Richard Mann said the injuries were of varying gravity with some suffering gunshot wounds and others cut by broken glass.
Mann said the shooter had not been taken to the hospital, because experts were checking his vehicle for explosives.
Witnesses said the shooter started firing at about 6:30 a.m. (1130 GMT) onto moving cars from an area near an apartment complex, media reports said.
“The shots were coming almost non-stop. Four, five, six at a time,” said Jaime Zamora, a cameraman for Houston television station KTRK who witnessed some of the shooting. He estimated that between 30 and 50 shots were fired.
Local stations broadcast images of cars with bullet holes and broken windows.
Emergency responders set up a staging area to help victims at a nearby strip mall.
Officials asked residents in the area to “shelter in place.”