At one point, the shooter ditched his vehicle and hijacked a US Postal Service truck, authorities said.
Law enforcement officers "trapped him in the parking lot of the Cinergy theater, and that's when they were able to engage him," Morales said.
Alex Wood told CNN he arrived at the theater complex and "next thing you know, I heard a pop, so, I flip the camera to where the theaters are and I just see a bunch of gunfire going off."
"I could see the officer walking up the mail van and discharging his weapon into it, and I believe that's when the shooter was killed," he said.
The conditions of those injured were not immediately known. Fourteen people were being treated at Medical Center Hospital in Odessa, Texas, according to CEO Russell Tippin. No ages or conditions were provided. The hospital has a family staging area with grief counselors and social workers to provide support, Tippin said.
This is the second mass shooting in Texas in August. Only four weeks ago, a gunman killed 22 people in a mass shooting in El Paso, located about 285 miles to the west of Odessa.
Democratic presidential candidate and Texas native Beto O'Rourke on Saturday reacted to news of this mass shooting by proclaiming, "We need to end this epidemic."
"Our hearts are with Midland, Odessa, and everyone in West Texas who has to endure this again. More information is forthcoming, but here's what we know: We need to end this epidemic," he tweeted.
Earlier in the day, Devin Sanchez, a spokesman for the City of Odessa, said someone in a gold Toyota was driving around shopping centers and shooting people from his vehicle.
The Odessa police Facebook page said the mail carrier truck was hijacked.
A law enforcement official told CNN that agents from the FBI's Midland office are responding to assist with the incident. The Midland office is a satellite office of the FBI's El Paso division.
The US Bureau of Alcohol, Tobacco, Firearms and Explosives in Dallas tweeted that agents would respond to the shooting.
Texas Governor Greg Abbott released a statement Saturday, saying:
"The First Lady and I are heartbroken over this senseless and cowardly attack, and we offer our unwavering support to the victims, their families, and all the people of Midland and Odessa. The state of Texas and the Department of Public Safety are working closely with local law enforcement to provide resources as needed and deliver justice for this heinous attack."
CNN's Amanda Watts contributed to this report.