HOUSTON – Police said Thursday they believe a single shot was fired Wednesday on the carnival grounds at the Houston Rodeo, but they have yet to find a witness to the shooting or to find a firearm on the rodeo grounds.

WATCH & LISTEN: VIEWER VIDEO OF POSSIBLE GUNSHOTS

Capt. Dwayne Ready, of the Houston Police Department, said a spent shell 9 mm casing was found in the northwest part of the carnival grounds, near Kirby and Westridge, which led them to believe a shot was fired.

"Our homicide division will continue the investigation with regard to any complainant or witnesses that we have to see if we can positively identify the person who shot that round," Ready said.

VIDEO: Officials provide update on investigation

Police said they arrested Raymond Colbert, 17, and charged him with evading arrest.

Ready said Colbert was arrested after he ran from officers who responded to the reports of gunshots.

"That's because he matched the description that was provided as a person who possibly fired the shot," Ready said. "When the officers went to make their approach he ran away."

He said police are still trying to determine if Colbert was the person who fired the shot.

Colbert is free on a $5,000 bond.

Reports of gunfire about 9:40 p.m. Wednesday created a chaotic scene at the carnival.

VIDEO: RodeoHouston attendees run after reports of gunfire

Video from witnesses to the panic showed people running out of the carnival. Some people claimed to have heard several gunshots, while others said they were just alarmed by the frantic crowd.

"We just saw some people running the opposite direction and asked, 'What are you running from?' And they said, 'There was a shooting!' And we just turned around and went the other way," Stacy Collins said.

Another viewer video appeared to record the sound of possible gunshots.

"I was surprised and scared. It just happened real quick," Jonathan Arias said. "It (the shots) was very loud."

An all clear was given about 10:35 p.m.

VIDEO: Scene outside RodeoHouston after reports of shots fired

Police said Wednesday that there was no evidence that shots were fired, and no injuries were reported.

Many rodeogoers told KPRC 2 that they were upset with how police and Houston Livestock Show and Rodeo officials handled the incident. Ready defended their actions.

"The information that we provided last night was accurate," he said. "We’re not tamping down anybody’s fear. We’re investigating what was reported, and to the extent that we can verify that, we'll do our due diligence."

Joe Cowley, president of the Houston Livestock Show and Rodeo, said Thursday that metal detectors are used at the gates in an effort to prevent weapons from being brought onto the grounds.

"We do prohibit open and concealed carry of firearms on our grounds," Cowley said. "The potential that a firearm was on our grounds is concerning."

Cowley said he believes the event’s security protocol is sufficient, but that the situation will be assessed and adjustments will be made if they are needed.

Ready said a weapon has not been found.

Houston police are asking anyone who witnessed the incident to call the Houston Police Department Major Assaults Division at 713-308-3600 or Crime Stoppers at 713-222-TIPS.