Andrew McCabe called the charges against the parents of Michigan school ...

Former FBI Deputy Director Andrew McCabe said the charges against the parents of Michigan school shooter Ethan Crumbley were 'unprecedented' but 'absolutely called for.'

On Friday McCabe told CNN's Ana Cabrera that he was stunned by Oakland County prosecutor Karen McDonald's involuntary manslaughter charges against James and Jennifer Crumbley, the parents of accused Michigan school shooter Ethan Crumbley, who are currently on the run from police. 

On Friday, McDonald revealed stunning details about the murder weapon: it was a Christmas gift for the 15-year-old, whom police say shot dead four students after penning a disturbing note saying 'thoughts won't stop, help me.' 

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'I was stunned when I heard that they were leaning in that direction because it's so exceedingly rare,' McCabe said. 'In the few states that have laws that address this sort of thing really no one ever gets prosecuted.'

But McCabe said after listening to the 'mountain of evidence' laid out by McDonald, he believes prosecutors will have a strong case and that what they presented was only just a sample of what they have so far.

McCabe stood behind prosecutors decision to move forward with charges against the Crumbleys and that he thinks this case will shine a light on school shootings. 

'It's incredible and it's absolutely called for,' McCabe said. 'and I think it maybe is just the sort of thing we need to attract attention to this epidemic of school violence.'  

McCabe said the case will be difficult to prosecute but that the case is strong.  

'This is an unprecedented prosecution, and proving criminally negligent or reckless homicide is tough under any circumstances,' McCabe said, but that he couldn't imagine 'a better perfect storm collection of fact and evidence to potentially hold these parents responsible.'

Hours after the charges were announced James and Jennifer Crumbley went on the run from police.

Police have issued a 'be on the lookout alert' and dispatched fugitive teams to search for the pair, who have until 4pm to turn themselves in. 

Oakland County Sheriff Michael Bouchard said he learned of the charges being filed against the Crumbleys from media reports and had no advance warning from the prosecutors, which could have allowed his agency to secure the suspects and prevent them from fleeing. 

McDonald alleged that the parents ignored multiple warning signs and refused to take their son out of school just hours before the shooting took place.

Jennifer bragged on social media about going out with Ethan to test his Christmas present - a 9mm handgun - just three days before the shooting at Oxford High School, and just one day after her husband James had purchased the gun for Ethan.

During a press conference Friday, McDonald revealed stunning new details leading up to the shooting that took place Tuesday afternoon, including that Jennifer texted her son about 30 minutes after the rampage saying, 'Ethan, don't do it,' and that her husband James called 911 to report that his gun - a 9 mm Sig Sauer SP 2022 - was missing and that Ethan was likely the shooter.

The prosecutor revealed that James, who - like his wife - has a prior criminal history, bought the murder weapon from a retailer with his son there on November 26. He stored the 9mm handgun in an unlocked drawer in his bedroom, McDonald said.

Less than a week before the gun was purchased, on November 21, McDonald said a teacher at Oxford High School observed Ethan searching ammunition on his cell during class and reported it to school officials.

Jennifer was contacted via voicemail by the school about her son's inappropriate internet search, and officials followed up with an email but received no

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