Oakland County Sheriff Michael Bouchard said at a press conference on Saturday afternoon that there is evidence that the 15-year-old sophomore student planned the attack in advance.
“We have clear evidence it was premeditated and he was actually looking forward to it,” he said.
The sheriff did not go into detail about the evidence. However, officials have previously revealed the contents of disturbing drawings, journal writings and social media posts made by the suspect in the days leading up to the attack.
His parents were called to the school twice this week prior to Tuesday’s attack – once after he was allegedly found searching for ammunition on his phone and the second time after he was found with drawing of a gun, bullet and victim with the words “blood everywhere”.
The teenager is accused of shooting dead four of his fellow students – Tate Myre, 16; Hana St. Juliana, 14; Madisyn Baldwin, 17; and Justin Shilling, 17 – and wounding one teacher and six other students in a shooting rampage at Oxford High School in Michigan on Tuesday.
He was arrested at the scene and has been charged as an adult with 24 counts including one terrorism charge and four counts of first-degree murder.
A motive for the attack is still unclear.
The teenager’s parents James and Jennifer Crumbley are also now behind bars after they were charged with four counts each of involuntary manslaughter on Friday.
The couple sparked a huge manhunt after they failed to show for their arraignment on Friday, before authorities found them hiding inside an art studio in Detroit close to the Canadian border early on Saturday morning and took them into custody.
Attorneys for the Crumbleys have claimed they were not on the run and were planning to turn themselves in, citing “a matter of logistics”.
Sheriff Bouchard cast doubt on these claims, given the circumstances in which they were discovered.
“Were they actually going to do it [hand themselves in]? I don’t know,” he said on Saturday.
“But given that they were hiding at a warehouse in Detroit it certainly raises eyebrows.”
He added that one of the suspects was seen by a witness smoking outside and “pretty much ran away”.
“Where they were and how they were seems to support the position that they were hiding and weren’t looking to surrender at that time,” he said.
The sheriff also suggested the couple’s actions reinforced their accountability over the shooting.
“If there was no culpability why would you be in a warehouse in Detroit?” he asked.
Judge sets $500,000 bond for James and Jennifer Crumbley
He didn’t rule out the possibility that extra charges could be filed against the parents in connection to their alleged attempts to evade justice.
The sheriff said that charges may also be brought against the individual who is said to have assisted the couple in hiding inside the warehouse building.
This individual, who has not been named, could face charges of either aiding and abetting or obstruction of justice, he said.
“We believe they were assisted in that location to get there, to get in and we are gathering that information and we will have the totality of that done fairly soon and present it to our prosecutor for potential charges for either aiding and abetting or obstruction of justice,” he said.
The sheriff said any charges will be determined by the Oakland County Prosecutor Karen McDonald at “some point in the near future”.
Authorities are asking anyone with information about both Tuesday’s shooting and the actions of the parents to come forward.
All three are currently being held separately and “in isolation” at the same jail and are not allowed to make contact with each other, he said.