RCMP arrested a student near the high school in in the community of Rossburn, Man., on Wednesday after a social media post showed the student holding a handgun.
Rossburn RCMP found out about the post around 1 p.m. Wednesday.
The school in the town, 275 kilometres northwest of Winnipeg, went into lockdown as a precaution and police quickly found the student. They found a CO2-powered replica pistol with ammunition.
No one was hurt and no other students are being investigated, RCMP said.
A 19-year-old man from Dauphin has been charged with possession of a weapon for dangerous purposes and carrying a concealed weapon.
More from CBC Manitoba: