CLEVELAND, Texas -

It's a scenario no one wants to think about -- an active shooter on a school campus. This week, students, staff and emergency responders at Cleveland High School rehearsed how they would react.

The drill simulated an active shooter still roaming the halls with many victims on campus.

With participants in make-up to look like blood and injuries and fake guns and real sirens, first responders got the chance to practice what they would do in a real school shooting.

"What we're doing is an active shooter mass casualty drill," said Cleveland ISD Police Chief Rex Evans.

Fire and EMS crews worked to help save victims' lives, and SWAT members entered the building to track down the shooter.

"What we're trying to do is maximize our saving of lives, so that we don't have victims bleeding out," Evans said.

Liberty County deputy and SWAT member Ranson Martel played the role of the shooter.

"Basically my job is to cause as many casualties as possible for the purpose of training the officers," said Martel.

Ken Defoor, captain with the Liberty County Sheriff's Department, says a live drill like this is the best training.

"The scenario with this one was a shooter came into the school, and in the process of going through the school shot and wounded a number of students and staff as well as one police officer," said Defoor.

The SWAT team came in to track down the suspect, a scenario that has followed the example of some actual school shootings where SWAT members had to walk past the wounded to try and to track down the suspect.

Hopefully they'll never need the skills learned during the drill.