A man who was stopped by Texas state troopers when his vehicle failed to signal a left turn opened fire and fled, engaging in a deadly shooting rampage before he was killed by officers outside a movie theatre, authorities said Saturday. Authorities said at least five people were dead and three law enforcement officers were among the injured.

The shooting began with an interstate traffic stop in the heart of west Texas oil country where gunfire was exchanged with police, setting off a chaotic afternoon during which the suspect hijacked a U.S. Postal Service vehicle and began firing at random in the area of Odessa and Midland, hitting multiple people.

Cellphone video showed people running out of the Cinergy movie theatre, and as Odessa television station KOSA aired breaking developments on live TV, their broadcast was interrupted by police telling them they had to clear the area.

Odessa is about 32 kilometres southwest of Midland. Both are more than 480 kilometres west of Dallas.

Police initially reported that there could be more than one shooter, but Odessa Police Chief Michael Gerke later said there was only one.

"Once this individual was taken out of the picture, there have been no more victims," Gerke said.

Gerke described the suspect as a white male in his 30s. He did not name him or a motive but said he has some idea who the gunman is.

Watch: Odessa police chief recounts timeline of shooting

Odessa Police Chief Michael Gerke provides an update on a shooting in west Texas that left at least five people dead and 21 injured. 6:07

The terrifying chain of events began when Texas state troopers tried pulling over a gold car mid-Saturday afternoon on Interstate 20 for failing to signal a left turn, Texas Department of Public Safety spokesperson Katherine Cesinger said. Before the vehicle came to a complete stop, the driver "pointed a rifle toward the rear window of his car and fired several shots" toward the patrol car stopping him. The gunshots struck one of two troopers inside the patrol car, Cesinger said, after which the gunman fled "and continued shooting innocent people," including two police officers.

Gerke said that, in addition to the injured officers, there were at least 21 civilians injured. He said at least five people died. He did not say whether the suspected gunman was included among those five dead.

The shooting comes just four weeks after a gunman in the Texas border city of El Paso killed 22 people after opening fire at a Walmart. Texas Gov. Greg Abbott this week held two meetings with lawmakers about how to prevent mass more shootings in Texas. He said he would visit the area Sunday.

The west Texas shooting Saturday brings the number of mass killings in the U.S. so far this year to 25, matching the number in all of 2018, according to The AP/USAToday/Northeastern University mass murder database.

Seven people remained in critical condition at one hospital hours after the west Texas shooting, said Russell Tippin, CEO of Medical Center Hospital in Odessa. He said a child under two years old was also transported to another hospital. He also said one person the hospital had received had died, although it was unclear if that victim was among the five dead that Gerke reported.

Tippin said 13 shooting victims were being treated at the hospital Saturday evening but he did not give their conditions or other information about the victims. Social workers and professional counsellors are at the hospital to provide support to the families of shooting victims, Tippin said. He also said the hospital has been locked down for that safety of the staff and patients.

A man prays outside of the Medical Center Hospital emergency room in Odessa. (Mark Rogers/Odessa American via AP)

"Right now the hospital is stable, it's secure," Tippin said.

Dustin Fawcett was sitting in his truck at a Starbucks in Odessa when he heard at least six gunshots ring out less than 45 metres behind him.

Watch: A man talks about fleeing the theatre in Odessa

Ethan Baeza, his brother and their mother had to evacuate a theatre in Odessa, Tex., because of gunfire nearby 1:49

At first, he thought it might have been a tire blowing out but he heard more shots and spotted a white sedan with a passenger window that had been shattered. That's when he thought, "Oh man, this is a shooting."

Fawcett, 28, an Odessa transportation consultant, "got out to make sure everyone was safe" but found that no one had been struck by the gunfire nearby. He said a little girl was bleeding, but she hadn't been shot, and that he found out she was grazed in the face.

Fawcett said authorities responded quickly and when police pulled out their rifles and vests he knew that "this is not a drive-by. This is something else; this is something bigger."

Police and sheriff's deputies surround the white van in Odessa. (Tim Fischer/Midland Reporter-Telegram via Associated Press)

U.S. Vice-President Mike Pence said following the shooting that President Donald Trump and his administration "remain absolutely determined" to work with leaders in both parties in Congress to take such steps "so we can address and confront this scourge of mass atrocities in our country."

Pence said Trump has spoken to the attorney general and that the FBI is already assisting local law enforcement.

Trump has offered contradictory messages in reaction to recent mass shootings. Days after the El Paso and Ohio shootings he said he was eager to implement "very meaningful background checks" and told reporters there was "tremendous support" for action. He later backed away from those changes, saying the current system of background checks was "very, very strong."

Most recently, Trump has called for greater attention to mental health, saying that new facilities are needed for the mentally ill as a way to reduce mass shootings. However, some mental health professionals say such thinking is outdated, that linking mental illness to violence is wrong, and that the impact of more treatment would be helpful overall but would have a minor impact on gun violence.