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.
The shooter was killed, after which police examined his body for explosives. They then examined his car and found numerous weapons, Montalvo said.
Authorities also planned to check his apartment, and asked residents in a three-block area to remain in their homes while police continued their work.
Witnesses told local media that the shooter fired onto moving cars from an area near an apartment complex.
"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.