The student accused of shooting two staff members at a high school in Denver, Colorado, before allegedly killing himself had been arrested for possession of a ghost gun two years earlier.
Denver Police said that the shooting unfolded just before 10am while Lyle was undergoing a daily weapons search at the school.
During the search, staff members located a handgun and Lyle allegedly opened fire, striking the two faculty members before fleeing the scene.
Following an hours-long manhunt to track down the student, Lyle’s body was discovered in a wooded area.
Now, the teenager’s past brushes with the law have come to light, revealing that he was still on probation for possession of a ghost gun at the time of Wednesday’s shooting.
Law enforcement sources told CBS Colorado that the 17-year-old had been arrested back in 2021 for possession of a ghost gun and a high capacity magazine.
His arrest came when he was a student at Overland High School and some fellow students reported photos on social media showing Lyle with a gun, the sources said.
A search of the teenager’s home then uncovered the ghost gun and magazine. He was later expelled from the school and began attending East High School.
As part of a school safety plan based on his prior behaviour, Lyle was required to be patted down for weapons each day on arrival at East High, Denver Police Chief Ron Thomas said at a press conference on Wednesday.
It was during this search that he opened fire.
“As part of a safety plan they were undergoing a search, as part of that search a weapon was retrieved, a handgun was retrieved, and several shots were fired, striking those two individuals,” the police chief said.
The two faculty members were rushed to hospital where Mr Sinclair remains in critical condition.
Mr Mason was released from hospital later on Wednesday after treatment.
Chief Thomas said at a press conference on Wednesday that the shooting had taken place in an office area in the front of the school, away from other students and staff.
He said that the school and law enforcement knew the identity of the shooter.
The school was plunged into lockdown and a manhunt was launched to track down the perpetrator.
A few hours on from the shooting, Denver Police identified Lyle as the suspect wanted on suspicion of attempted homicide.
Members of the public were warned that the student – who was wearing a hoodie with an astronaut on it and was believed to be in a 2005 red Volvo XC90 with a Colorado licence plate – should be considered “armed and dangerous”.
Not long later, the car was located and Lyle’s body discovered nearby.
Park County Sheriff Tom McGraw said on Wednesday night that police had located a male body in some woods close to the abandoned red Volvo.
The sheriff said that the body had not yet been identified as belonging to the student but a shelter-in-place was lifted for residents in the Park County area.
On Thursday morning, the county’s coroner’s office confirmed that the body was that of Lyle.
An autopsy will now be carried out to determine cause and manner of death.
A law enforcement source told 9NEWS that Lyle appeared to have died by suicide.
Wednesday’s shooting marks just the latest gun violence to rock the high school in the space of a month.
In February, 16-year-old student Luis Garcia was shot as he sat in a parked car close to the school grounds.
He died weeks later.
Following his death, a group of fellow students called on local officials to take action to make their schools safer.
Several attended a city council meeting and spoke on their fears over gun violence in schools while the Denver East High School chapter of Students Demand Action staged a walkout demanding better gun control.
So far in 2023, there has been at least 18 shootings resulting in at least one injury or death at elementary or secondary schools across America, according to the Gun Violence Archive.
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