Two people were killed, six were injured and a 17-year-old was arrested after gunfire broke out overnight in downtown Orlando, Florida, where tens of thousands were gathered to celebrate Halloween, state officials said.

Orlando Police Chief Eric Smith said officers responded to shots fired around 1 a.m. Friday in the area of Central Boulevard and Orange Avenue before police witnessed a second shooting about a block away, near Washington Street and Orange Avenue.

Eight people were shot, including two who were pronounced dead, and six who were rushed to Orlando Regional Medical Center, where they are in stable condition, Smith said. The victims, none of whom have been named, range from ages 19 to 39.

Police at the scene of the second shooting arrested a 17-year-old suspect. Smith said it's unclear if the alleged shooter knew the victims and said police were investigating a motive.

"This is still an active investigation. As we gather more information, we will provide you with another update," he said.

Police released dramatic surveillance footage showing thousands of people on Orange Avenue when the suspect approached one of the victims and fired a handgun, creating pandemonium as the crowd reacted to the shots and people fled in all directions. Within seconds, at least eight officers surrounded the victim.

A few minutes later, video captured the suspect rushing into a throng of people before additional shots were fired and another chaotic scene unfolded. As the suspect began to leave, videos show one of the officers who had witnessed the shooting force the teen to the ground.

The incident occurred on one of the city's busiest nights of the year, Smith said. Between 50,000 to 100,000 people, many wearing costumes, packed the streets of downtown Orlando to celebrate Halloween. About 100 officers provided security for the event.

"Most people are down there to have a great time, and, of course, you always have those people who come down there who have different things on their mind," Smith said.

State Attorney of Orange and Osceola counties Andrew Bain said the case has not yet been turned over to this office. Based on evidence, he said the teen could be charged as an adult.

"There's several aggravating factors that would lean us to charge him as an adult, but we need to get to the bottom of the investigation first," he said at a news conference early Friday.

The assault was one of at least 439 mass shootings in the U.S. this year, according to the Gun Violence Archive, a nonprofit that defines mass shootings as incidents involving four or more victims.

What we know:2 killed, 6 injured in Florida Halloween crowd shooting

(This story has been updated to add new information.)