The repeated threats have closed the entire school division in Manitoba, forcing nearly 4,000 students in 15 schools north of Winnipeg to stay home Monday.
The initial online threat that appeared on Sunday triggered a message from Lord Selkirk to the school, saying a Selkirk high school would be closed.
But, a few hours later, the division announced that the CCHR arrested a person and the threat ended. A recorded message sent to the parents stated that the school will actually be open on Monday.
However, the second threat appeared on social media late last night and resulted in the abolition of two more people, for a total of three arrests.
This prompted the division to publish a message on its website early Monday, stating that all of its schools would be shut down "to ensure student and employee safety," while RCMP continues to explore.
"When it comes to security, you just do not want to take any chances until we know all the information from the RCMC," said Michele Polynuk, division supervisor, for CBC News.
The department uses an online messenger system to warn parents and students for any great information, but did not work on Monday morning, she said.
"We count on the media to extract the information. We also send mass messages … so that they know that our schools are closed."
The departmental schools serve the town of Selkirk, the communities of Lockport, St. Andrews, Clandeboy, Petersfield and Libya and the coastal communities of Grand Mare and Victoria Beach.
Polunuk knows nothing about the people who made threats – if they are current or former students from the division.
Further updates on the situation will be posted on the school's website.