The 17-year-old suspect in a shooting last week that killed two people and injured eight during Halloween celebrations in downtown Orlando, Florida, has been charged as an adult, authorities said.

Jaylen Dwayne Edgar was charged as an adult with two counts of second-degree murder with a firearm and one count of attempted murder with a firearm, State Attorney Andrew Bain said Monday. The case will be presented to a grand jury, which could decide to elevate the charges to first-degree murder, Bain said.

Edgar will face additional charges as the investigation continues, authorities said.

"This decision was not made lightly and only after a review of all available evidence," Bain said in a statement Monday. "I have personally reviewed all available records and video evidence in this case and there is no question this individual should be charged as an adult."

The Orlando Police Department estimated about 75,000 people were gathered in downtown Orlando to celebrate Halloween last week when gunfire broke out overnight. Early Friday, two people were killed and seven were wounded by gunfire, authorities said.

Another person was hospitalized after being trampled on while trying to run to safety, Bain said. The victims were ages 19 to 39, according to Orlando Police Chief Eric Smith.

Bain said responding police officers immediately identified Edgar as the gunman and "took him into custody moments after the shooting." Prosecutors were working with the Orlando Police Department and have asked the public to submit any videos or pictures from the night of the shooting.

"To shoot into a massive crowd like that shows a total disregard for life and the only recourse is to charge the defendant as an adult because it fits the egregious nature of the crime," Bain said in the statement.

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What happened in the downtown Orlando shooting?

According to Smith, 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,

A total of nine people were hit by gunfire, in which two were pronounced dead, according to police. The six victims who were wounded were taken to the Orlando Regional Medical Center and were in stable condition, Smith said.

Another person who suffered a gunshot wound took herself to a local hospital, police said.

Police released surveillance and body-camera footage showing a crowd of thousands of people in the streets when the suspect opened fire, causing chaos as people fled. Within seconds, at least eight officers surrounded the person who was shot.

A few minutes later, footage captured the suspect rushing through the crowd before additional shots were fired. Officers apprehended the suspect when he tried to leave the scene.

Authorities said the shooting occurred on one of the city's busiest nights of the year as tens of thousands of people gathered to celebrate Halloween. About 100 officers were in the area at the time to provide security, Smith said.

The incident was the latest mass shooting in the United States. At least 445 mass shootings have occurred this year, according to the Gun Violence Archive, a nonprofit organization that defines mass shootings as incidents involving four or more victims.

Contributing: Gabe Hauari and Christopher Cann, USA TODAY; C.A. Bridges, USA TODAY NETWORK - Florida