Nineteen-year-old Matthew Milby was just days away from graduating high school when authorities say he came out of a bathroom with a gun and opened fire at Dixon High School.
Milby, who was injured in a shootout with a school resource officer, was released from the hospital Thursday morning and processed into the Lee County Jail, according to police. He was already charged with three counts of aggravated discharge of a firearm, all class x felonies, in connection with Wednesday's shooting.
His bond was set at $2 million, city officials said.
"More charges may be filed in the near future," a Facebook post from the city of Dixon read.
Students were not expected to be in attendance at Dixon High School Thursday as the investigation into the shooting at graduation practice continued.
Roughly 180 students were in the school's gymnasium to practice for graduation at around 8 a.m. on Wednesday when authorities say Milby - one of the seniors graduating - began shooting.
School resource officer Mark Dallas rushed at Milby, officials said, in an effort to protect the students - including his own son.
As Milby was running away, authorities said he was firing at Dallas, who returned fire, striking Milby in the shoulder before arresting him.
As Dallas chased Milby, school officials said students were barricading themselves in classrooms as they had been trained to do, while others ran.
"(A) teacher peeks out of a doorway and he comes in and I seen his face he says, 'Everybody get out of here, go, go,” student Brandon Stehl recalled after the shooting.
School officials and law enforcement alike praised Dallas as a hero for his quick action, crediting him for saving countless lives.
"Our kids did a fantastic job, our staff did a fantastic job, our resource officer did a fantastic job," school principal Mike Grady said at a news conference. "It was a situation where this is the best possible outcome we could have."
The alleged gunman's mother Julie Milby said her son was bullied and that she had no idea he had the gun - which belonged to her but was kept at her 91-year-old grandfather's house - until after the shooting.
"I wouldn't have dreamed he would do this in a million years," she said, adding that before the shooting, her family was excited for her son to graduate on Sunday.
Police said an investigation revealed Milby's mother purchased the gun in 2012. They are still working to find out how the teen "obtained access to the weapon."
An investigation remained ongoing Thursday.