DENVER (KDVR) New information is coming out about the tragic event last Wednesday at Evergreen High School, where a 16-year-old student was responsible for a shooting that left two students critically injured and ended with his own death.

The Jefferson County Sheriff’s Office reported that the first deputy was sent to the scene at 12:24 p.m., shortly after 911 began receiving numerous calls. Deputies reached the high school in roughly two and a half minutes, during which the shooter had discharged several bullets inside Evergreen High School, injuring a student in the process.

“Despite the rapid response of the deputies, the quick actions of teachers, staff, and students inside the school undoubtedly prevented further harm,” stated the sheriff’s office. “They effectively implemented safety protocols and lockdown procedures they had rehearsed, and these immediate measures were crucial in making a difference.”

Earlier that day, a part-time school resource officer was on campus but was summoned away to assist with a nearby accident. The Jefferson County Sheriff’s Office noted that the deputy adhered to standard protocol, and also announced that a full-time officer will be stationed at the school when classes resume.

The agency explained that shooter Desmond Holly left the main school building, traversed the football field, and shot another student at the intersection of South Olive Road and Buffalo Park Road.

As of Tuesday, one student at Saint Anthony’s Hospital was still in critical but stable condition, while the other, who was taken to Children’s Hospital Colorado, remained in serious condition.

Then, deputies located and confronted Holly, “who then took his own life.” The agency said that there was one shooter in the incident, and approximately 20 rounds were fired. Officials have said they do not know how Holly got hold of the gun.

The Jefferson County Sheriff’s Office said that most school shootings end in minutes, with federal studies showing that active shooter events end in five minutes or less. That timeframe for school shootings is closer to 10-12 minutes, according to the sheriff’s office, and the incident at Evergreen High lasted nine minutes.

“Our hearts are heavy for the two students who were wounded and for the trauma this community will carry long after today,” the sheriff’s office said. “At the same time, we are deeply grateful for the courage and calm shown by Evergreen High School students, teachers, administrators, and staff. Their training, quick thinking, and resilience helped prevent an even greater tragedy.”

The sheriff’s office investigation into the shooting is ongoing. Last week, the agency said that Holly had brought “quite a bit” of ammunition to the school along with a revolver.

Holly’s actions inside the school were tracked through security cameras. Some students were at lunch at the time of the shooting, while others were in the hallways and outside the school building. When gunfire started, some students ran away, while others found areas to lock down.

Law enforcement says that Holly tried to access areas that were locked down but could not enter.