Texas high school shooting

11:09 a.m. ET, May 18, 2018

Sheriff confirms "multiple casualties" in Texas school shooting

Harris County Sheriff Ed Gonzalez confirmed on Twitter that this is no longer an active situation, but added there are multiple casualties.

Here's the tweet:

10:54 a.m. ET, May 18, 2018

There have been multiple fatalities, sources say

There have been multiple fatalities at the shooting at Santa Fe High School, two law enforcement sources told CNN, citing preliminary information.

The scene is still being processed and cleared, the sources said.

10:20 a.m. ET, May 18, 2018

There are confirmed injuries. The situation is contained.

A Facebook post by the Santa Fe School District states that "the situation is active, but has been contained."

It adds that "there have been confirmed injuries."

Here's the post:

This morning an incident occurred at the high school involving an active shooter. The situation is active, but has been contained. There have been confirmed injuries. Details will be released as we receive updated information. Law enforcement will continue to secure the building and initiate all emergency management protocols to release and move students to another location. All other campuses are operating under their regular schedules....The district will continue to keep you updated as information is available. Safety and communication are our top priorities.

10:19 a.m. ET, May 18, 2018

First, she heard a fire alarm. Then her principal told her to run.

MaKenna Evans, a 16-year-old sophomore at Santa Fe High School, told CNN she was in geometry class when the shooting started.

First, she heard the fire alarm, she said. When the students got outside, her principal told them all to run.

Evans said students hid behind a building across the street from the school. Her aunt called and told her there was a shooting. (Her aunt's husband is a police officer and he'd told her what had happened.)

Evans' brother picked her up, and she is now safe at home.

10:11 a.m. ET, May 18, 2018

Assistant principal says a person has been arrested

Dr. Cris Richardson, assistant principal of Santa Fe High School tells reporters that there was an active shooting at the school, and "that person has been arrested."

"We have done an amazing job to get the students out of the building safely and to reunited them with parents as we are able to and that's about all I can tell you right now," Richardson said.

Richardson could not comment on injuries.

10:03 a.m. ET, May 18, 2018

At least 3 helicopters seen waiting in school parking lot

At least three helicopters have landed in the school's parking lot, video from CNN affiliate KTRK just shows. Officials were just seen wheeling a stretcher toward one of them. It isn't clear if an injured person is on the stretcher.

Patients from Santa Fe High School are currently en route to University of Texas Medical Branch in Galveston, according to Raul Reyes Director of Media Relations for University of Texas Medical Branch.

The total number of patients is unknown at this time.

9:55 a.m. ET, May 18, 2018

Student: We assembled outside for a fire drill, then we heard gunshots

A Santa Fe High School student described the moment they all heard gunshots.

"So, it was just a normal-like class day. We all were doing our work in first period. And then all of a sudden like it's a fire drill," 14-year-old junior Angelica Martinez said.

"So we followed the fire drill procedures. And then we went outside. Like we were all standing there, but not even five minutes later, we all start hearing gunshots."

That's when everybody starts running, she said, despite teachers telling them to "stay put."

"But we're all just running away."

Listen: