ODESSA, Texas -- Authorities have identified the gunman who opened fire at random in the West Texas city of Odessa as 36-year-old Seth Aaron Ator.
As federal agents join the investigation into why this mass shooting happened, we have learned more about the gunman.
Odessa police say the death toll is now seven after Ator was stopped by state troopers opened fire and fled, shooting people at random.
Authorities spent Sunday combing through more than 15 crime scenes and searching Ator's home and car.
Still working to determine the reason behind the shooting, authorities tell ABC13 he used an AR-style weapon during the 10-mile long shooting spree.
Odessa police spokesman Steve LeSueur said Sunday that at least one person remains in "life-threatening" condition.
The shooting set off a chaotic afternoon in which police reported that a suspect hijacked a U.S. Postal Service vehicle and began firing at random in the area of Odessa and Midland, hitting multiple people. Police initially reported that there could be more than one shooter, but Odessa Police Chief Michael Gerke says authorities now believe it was one shooter.
Saturday's horror ended in the parking lot near the Cinergy movie theater where he shot two police officers before being gunned down.
At this time, police do not believe this was part of a terroristic plot.
Throughout the weekend, Midland Memorial Hospital said it received six patients connected to the shooting, three of whom were in critical condition. Medical Center Hospital in Odessa received 13 patients, including one who has died, seven in critical condition, two in serious condition, two who were treated and released and one child under the age of 2 years old who was transferred to another facility in North Texas for further care.
A Midland officer, an Odessa officer, and a DPS trooper were among the injured. The trooper's injuries were non-life-threatening, Midland Mayor Jerry Morales told CNN, and the Midland officer underwent surgery.
Odessa is about 20 miles southwest of Midland. Both are more than 300 miles west of Dallas and lie along Interstate 20 approximately at the midpoint between El Paso and Fort Worth.
ABC News and the Associated Press contributed to this report.