Metro Police said they arrested the masked gunman who was seen at the Boulevard Mall Thursday night.
Police said they recovered the mask and the gun, which "appears to be fake." He was not identified.
Police surrounded the mall, which was "completely evacuated." Police said they received video of the man carrying a long gun inside the mall.
No citizens were injured and no shots were fired by the suspect as of 8:24 p.m. Thursday, Metro Police said. The mall was evacuated "while officers ensure the suspect is not inside," Metro Police said.
Metro said they have conducted four searches and have been unable to locate the man. They were using their tactical team and K9 to try to find him.
Police said it was not an active shooter situation and they did not know the man's intent.
Streets were closed in the area but have since reopened. As of 10:30 p.m., police said they did not believe the gunman was still inside the mall and "people in the area should not be concerned." They also said people can return to the mall to get their cars parked there.
Witness Cory Mathews shared his experiences.
"We were just celebrating my son's birthday at the rec center: bumper cars, golf, rock climbing, laser tag, we heard some commotion going on. Three minutes later police came in with guns. First they told us to get to a safe place, and they told us to put our hands up, and escorted us out."
"(Seeing armed officers) you just hope everything is alright, it's obviously something to be concerned about. My concern really is, for my children. You want to make sure everything is going to be ok. I hope no one's hurt."
"If (the kids) didn't see me panic, they wouldn't panic. I guess that's kind of the good thing about it. If I had shown any kinds of fear, something like that" "We did hear some noise, but what we heard was the police, had to get into an area where we would be safe."
"At least 10 officers had their guns drawn, they were looking for someone." "Snipers (had) handguns, shotguns, they have some artillery."
"I'm just praying everything is ok, that there is no casualties, no one really harmed, just praying that everyone makes it out safely tonight."
"First there was a little confusion, but for the most part people were pretty calm, you can extinguish times for being stalling and afraid, it makes you want to stand still and you know what I mean.
Many officers had guns drawn as they were stationed outside the mall on Maryland Parkway near Desert Inn Road, just north of UNLV.