SACRAMENTO, Calif. (KTXL) — Police said a second person has been arrested as they investigate the mass shooting in downtown Sacramento.

Smiley Martin, 27, was hospitalized with serious injuries after he was hit by gunfire at the scene of the shooting on K and 10th streets, police said.

He has been under the supervision of an officer and once he is discharged from the hospital, the police department said he will be booked into the Sacramento County Main Jail. Martin faces charges on suspicion of being a prohibited person in possession of a firearm and possessing a machine gun.

A law enforcement official told the Associated Press that Martin had posted a live Facebook video of himself brandishing a handgun hours before gunfire erupted early Sunday morning. Authorities are trying to determine whether the weapon seen in the video was used in the shooting, said the official, who was briefed on the investigation but could not discuss details publicly and spoke to AP on condition of anonymity.

A year ago, prosecutors implored the state parole board not to release Martin early from a 10-year sentence, noting his prior convictions for possessing an assault weapon, stealing electronics from department stores and beating a girlfriend he encouraged to be a prostitute.

“Martin’s criminal conduct is violent and lengthy,” a Sacramento prosecutor wrote in a letter obtained by AP. “Martin has committed several felony violations and clearly has little regard for human life and the law.”

Martin’s 26-year-old brother, Dandrae, has already been arrested as a “related suspect.”

“At this point we believe that Dandrae and Smiley were together when the shooting occurred,” said Sgt. Zach Eaton, with Sacramento police.

Dandrae Martin faces felony charges on suspicion of assault with a deadly weapon and being a convicted person carrying a loaded firearm.

“This individual has not been arrested for any homicide related to this incident. The investigation is highly complex involving many witnesses, videos of numerous types and significant physical evidence. This is an ongoing investigation and we anticipate more arrests in this case,” said Sacramento County District Attorney Anne Marie Schubert about Dandrae Martin’s arrest.

Dandrae Martin has been held without bail and is expected to appear at the Sacramento County Superior Court at 3 p.m. Tuesday.

Investigators believe the brothers possessed stolen guns and are working to review financial documents, call records and social media messages to determine how and when they procured weapons, the official said.

“We believe that handgun belonged to Smiley Martin,” Eaton said.

Eighteen victims were wounded early Sunday morning, sparking chaos in an area of downtown known for its nightclubs and entertainment scene. Six people died.

At the scene, investigators said they found over 100 shell casings and a stolen handgun that had been converted into an automatic firearm.

SWAT team members and detectives have since served search warrants at three local homes.

Sacramento Mayor Darrell Steinberg thanked Sacramento officers following both arrests.

“Thank you to all the hardworking officers in the @SacPolice who have worked so methodically and quickly to apprehend suspects in this horrific shooting,” the mayor tweeted early Tuesday morning.

The Sacramento Police Department is gathering video and photo files from witnesses through its evidence portal. A QR code was also created for people who may have captured the mass shooting on their smartphones.

This story is developing. Check back for updates.

The Associated Press contributed to this report.