McEachern High School in Powder Springs was under a Code Red lockdown earlier Thursday afternoon after a shooting not involving students.

COBB COUNTY, Ga. — A Cobb County high school was put on a code red earlier Thursday after a shooting involving non-students happened in a campus parking lot. The students have since been able to be dismissed after police assessed the school was safe. 

According to the school district, some schools in the area were temporarily placed under a Code Yellow because of this incident, but all have now resumed normal operations. 

RELATED: McEachern High School 'secure' after 2 non-students shot in parking lot

The shooting was reported Thursday afternoon at McEachern High School in Powder Springs. Two people who were not current students had been shot in the parking lot and are expected to survive. 

But what does a Code Red and other alerts mean for the Cobb County School District? 

During an Alert 

A Code Red is considered to be a lockdown where immediate action is required, according to the district. This means the doors are locked, the lights are off and everyone should immediately get out of sight. This is the highest level of alerts.

Code Yellow is a lockout where all the exterior building doors are locked and the blinds on exterior windows are lowered.

A Code White is a weather alert, so people must be prepared to seek shelter and be prepared for any further instructions. 

A Code Blue is when those need to stand by for further instructions. 

And finally, a Code Green is when schools can resume normal operations.

A Cobb County educator sent 11Alive the following photo that is posted inside schools that describes the meaning behind each code.

Cobb County Police Chief Stuart VanHooser said that in Thursday's incident, there was never an active shooter, the campus was secured and the students were safe. 

"I will say this -- when we get these calls, we don't know if it's an active shooter or not, and so our officers treat it as if it is an active shooter," VanHooser said. "We train for this...every single year in Cobb County, and we know how to handle these." 

According to the Cobb County School District, there are unannounced Code Red Drills, which "allow for a 'snapshot' of a school's preparedness of a Code Red Lockdown, with a follow-up debriefing and discussion for administrators."