The teacher told students he would've pulled a smoke detector, according to one parent.
A judge in Michigan imposed a combined $1 million bond on the couple.
A Michigan teen faces a 20-year felony charge after admitting to posting a threat that included a firearm image, police said on Friday.
The Oakland County sheriff strongly criticized the county's prosecutor after the couple evaded custody.
"We did not know these charges," the sheriff stated.
One person on Twitter asked if the situation "could get anymore messed up."
The parents of the teen accused of killing four fellow students went missing hours after they were charged with four counts of involuntary manslaughter.
"We want to praise the students who spoke up and let school administration know about the situation," a junior high school principal said.
Oakland County Sheriff Michael Bouchard said the attorney of James and Jennifer Crumbley could not get a hold of the couple after the charges were issued.
Burke County Sheriff Williams told Newsweek his office was working with state and federal authorities to determine the person responsible for the threat.
"Making a false threat of terrorism is a felony and could result in 20 years imprisonment," police reminded parents and students on Friday.
An analysis by Newsweek found that 519 schools closed on Friday as string of copycat threats of violence were made in seven different states.
The Oakland County Prosecutor said drawings found on Crumbley's desk contained a semi-automatic handgun pointing at the words "the thoughts won't stop help me."
Crumbley has been charged with four counts of first-degree murder after the death of four students at Michigan's Oxford High School on Tuesday.
Schools have been closing across the country since the Oxford High School shooting took place on Tuesday, which killed four people and injured eight more.
Though Crumbley has already been charged with two dozen crimes, Oakland County prosecutor Karen McDonald is also weighing criminal charges against the parents.
School districts in the Detroit area have reported receiving threats of violence on social media following the shooting at Oxford High School that killed four.
Cameron Kasky reflected on the key role he's taken on in the youth-led movement on gun violence prevention, writing "I wish I could have done it all right."
Sports and political commentator Keith Olbermann is being criticized for politizing the Michigan school shooting.
"We can't do nothing," Senator Rosemary Bayer, a Democrat who represents the district Oxford High School is located, said. "We have to take action."
The video of the shooter trying to trick the students have been viewed over 2.5 million times.
The Oakland County Sheriff said they had no knowledge about the online threats against the school prior to the shooting.
Senator Chris Murphy argued the issue of making schools safer is something both Republican and Democrat voters can agree on.
Oakland County Sheriff's Office said the 15-year-old arrested after three students were killed at a Michigan high school had "posted pictures of the target and the weapon."
One adult died and at least three others were injured in the shooting at Humboldt High School.
The 15-year-old is facing charges of endangerment, aggravated assault, and weapons violations relating to bringing a weapon on campus.
Eight individuals were receiving treatment Tuesday evening for injuries they sustained during the shooting, authorities said.
Authorities said they received over 100 calls Tuesday afternoon about the active shooter incident at the high school.
"I'd like to be able to move on from ever thinking of him again," said Guttenberg, whose 14-year-old daughter died in the 2018 school shooting in Florida.
Aurora Police Chief Vanessa Wilson told reporters that the three injured students are expected to survive.