UPDATE: At 1:58 p.m., Arlington Police updated that the suspect had been taken into custody without incident.
An active shooter at Timberview High School near Arlington left four injured, according to the Dallas Morning News and other media sources.
Police have identified 18-year-old Timothy George Simpkins as a possible shooter, media reports.
Police believe Simpkins is driving a 2018 silver Dodge Charger with Texas license plate PFY-6260, police stated.
Police say if you encounter the vehicle or person, do not approach, but call 911 as Simpkins is believed to be armed.
News sources report multiple different possible causes of the shooting.
The Texas Department of Transportation said drivers should expect delays on State Highway 360 near Debbie Lane.
Timberview High School is a part of the Mansfield Independent School District.