It was a scary situation for hundreds of students.
Grand Junction High School was having a normal school day before students spotted a man with a gun a little before 9 a.m. Wednesday morning.
The school was locked down, police were called and students waited with little information on what was happening outside.
Anthony Gallegos was in his food science class when it happened.
"We do a lot of drills, like fire drills, and shelter-in-place and lockdown; just figure out what to do in case there was a threat," said Gallegos.
Students weren't sure if this was real or not.
"Nobody was really nervous in my classroom because we thought it was a drill, but everybody still reacted as though it wasn't, just because teachers take it really seriously and stuff; so of course we have to," recalled Gallegos.
As it turns out, a man was riding his bike near the school, sporting a visible weapon.
"His handgun became unconcealed as he was riding his bike, and that's when the student saw it," said Sergeant David Krouse with the Grand Junction Police Department.
The student did the right thing and alerted the authorities.
"Given some of the incidents that have happened around the country at different kinds of locations at schools and hospitals, people just need to be aware that people are on the lookout for any threats, as they should be, and are going to report those; so people need to be extra cautious," warned Krouse.
In Colorado, if you lawfully own a gun, you can carry it on your person; but if you cover it up, you must obtain a valid permit. The man didn't do anything illegal because he had a valid concealed handgun permit.
"The piece here is just good common sense and good judgment," said Lieutenant Phil Stratton with the Mesa County Sheriff's Office.
According to Stratton, it isn't a good idea to carry a gun near an institution like a school.
"Don't carry a weapon on school grounds. There's really no legitimate reason to. Don't take a gun anywhere that's going to cause undue concern or alarm," said Stratton.
And understand the responsibility of owning a gun.
"It's not to be cool, it's not to look good or for fun; it's a huge responsibility that a lot of people need to realize there's a time and a place," said Stratton.
Wednesday, it was the wrong place and wrong time.
"It turned out that everything was ok, and the police tracked him down, and it wasn't a big deal," said Gallegos.
School District 51 does lockdown drills specifically to prepare students for situations like this, and police encourage you to always report anything suspicious near a school.
Police say if you report an incident in good faith, you aren't doing anything illegal.