Two Arlington Heights High Schools students are under arrest, police say, after one fired a gun during an off-campus fight and another was in possession of an air pistol on campus.

The high school was placed on lock down Thursday afternoon after a student at a McDonald's restaurant adjacent to campus pulled out a gun and fired it during a fist fight.

NBC 5 learned at least two people were fighting outside the restaurant while a larger group watched. No one was injured when the group watching the fight scattered as one shot was fired into the air, police said.

After the shooting, police said the teen is believed to have discarded the gun. At this time, the gun has not been found.

As the investigation unfolded, police said a gun found on campus by a school resource officer was the one fired after the fight. Police now say the gun found in the high school is a CO2 air pistol and not the one discharged outside of the McDonald's restaurant.

Two students were arrested Thursday, after Fort Worth police say one fired a gun near Arlington Heights High School and another was found to be in possession of an air pistol on campus.

Police confirm two people are in custody, the one believed to have fired the shot and the one in possession of the CO2 air pistol found on campus. The individuals, whose identities and ages have not been released, are students at Arlington Heights High School. Police said the student who fired the gun is expected to face a deadly conduct charge and the student who took the gun onto campus is expected to face a charge of having a gun in a gun free zone.

A student at the restaurant when the fight broke out told NBC 5 just how scary the situation was when he saw the teen pull out the gun.

"After ordering my food I saw a big crowd coming in, and I was like, 'Whoa, they’re fighting outside.' Then I saw somebody pull out a gun, and I was like, 'Oh my god, they have a gun!' Then police came and everybody started running. It was really crazy," said 16-year-old Gary Clark, a junior at AHHS. "All I could do was run. I ran for my life, literally. Like I couldn’t do anything here at the McDonald's, so I ran and was telling everyone else there was a gun out here."

NBC 5 News

Clark said he was scared because at any point the teen could have aimed his way or accidentally fired into the restaurant.

"I was scared. I wanted to cry," Clark said. "I know everybody is going to be talking about it and there’ll be more drama tomorrow than there already was."

At 3:40 p.m., students were dismissed from campus on time.

The investigation into the shooting is ongoing and police have revealed no further information.

Fort Worth’s Arlington Heights High School was placed on lock down Thursday afternoon after a student involved in a fight fired a weapon at an off-campus restaurant, police say.

NBC 5's Chris Van Horne contributed to this report.