At least eight people have died as a result of a shooting Friday morning at a high school in the southeastern Texas city of Santa Fe, CNN affiliates are reporting. This is the third school shooting in eight days, and the 22nd since the beginning of the year in the United States.

A suspect has been arrested in Friday's shooting at Santa Fe High School, about 20 miles outside Galveston, assistant principal Cris Richardson told reporters near the school.

A second person has been detained as well, Harris County Sheriff Ed Gonzalez.

Witnesses described students running from the school as they heard gunshots; they also described hearing an alarm at the school, though the sequence of events wasn't immediately clear.

Students empty their backpacks outside Santa Fe High School Friday.

An armed person walked into an art class at the school and began firing what looked like a shotgun.

The witness told KTRK she saw a girl shot in the leg.

Multiple deaths have been reported as a result of the shooting, two law enforcement sources told CNN.

Patients from the school are being taken to a hospital in Galveston, hospital spokesman Raul Reyes said. He did not say how many or give details about the injuries. At least one police officer was injured, Sheriff Gonzalez said.