Video shows Oxford High School students realizing they may have been speaking to the gunman when a person outside their classroom called them 'bro'

• A shooter killed three people at Oxford High School in Michigan on Tuesday.
• A video shows students speaking to someone outside the classroom who claimed to be a sheriff's deputy.

A video taken at a Michigan high school shows the moment students realized they could have been talking to a gunman who was impersonating a sheriff's deputy after the person talking to them from outside their classroom called them "bro."

A shooter killed three students between 14 and 17 years old and injured several others at Oxford High School on Tuesday, the Oakland County Sheriff's Office said. A suspect, identified as a 15-year-old sophomore, was taken into custody, officials said.

The video, taken inside a classroom, showed students evacuating through a window after hearing the person at the door say "bro." It was not clear whether the person was the gunman.

The video was taken by a student who shared it with his father, Fox 2 Detroit reported.

In the video, the person behind the door can be heard saying: "Sheriff's office. It's safe to come out." A student can be heard replying, "We're not willing to take that risk right now."

"I can't hear you," the person behind the door says. A student says again, "We're not taking that risk right now."

"Come to the door and look at my badge, bro," the person behind the door can be heard saying.

One student can be heard telling classmates: "He said 'bro.' Red flag." Another can be heard saying, "Window," and the students start to exit.

Oakland County Sheriff Michael Bouchard said on Tuesday night that officials had been told that the gunman pretended to be law enforcement to try to gain access to barricaded classrooms.

In a Facebook post, the sheriff's office identified the victims as Tate Myre, 16, Hana St. Julian, 14, and Madisyn Baldwin, 17.

In another post several hours earlier, the sheriff's office said the shooter had used a 9 mm Sig Sauer handgun that "had been purchased by the father four days prior to the incident."