According to police in Arlington, Texas, a suburb of Dallas, multiple people have been wounded in a school shooting at Timberview High School. (See early coverage from WFAA-TV below)

The Dallas Morning News reports:

The school is on lockdown, Mansfield Independent School District said in a news release.

Multiple people have been taken to hospitals, police said. Arlington police said authorities were conducting a methodical search of the school.
Reports from NBC News say four people were injured, three taken to local hospitals.
Live coverage can be seen here:
This is a developing story and will be updated.