A second person was arrested in connection with the deadly mass shooting early Sunday morning that took the lives of six people and injured a dozen others, according to the Sacramento Police Department. Leer en españolThe second suspect was identified as 27-year-old Smiley Martin, who was taken into custody Tuesday on charges that include possession of a firearm by a prohibited person and possession of a machine gun. He had posted a live Facebook video of himself brandishing a handgun hours before gunfire erupted, a law enforcement official told The Associated Press.Smiley Martin is the brother of the first suspect arrested, 26-year-old Dandrae Martin, police said. Smiley Martin sustained serious injuries from the shooting and is currently in a nearby hospital for treatment. He will be booked into the Sacramento County Main Jail once he is released from the hospital. Police confirmed Dandrae was also injured during the shooting.Authorities are trying to determine whether the weapon seen in the video posted on Smiley Martin's account 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.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.Martin has had run-ins with the law in Sacramento County since at least 2013. In a letter last year to the Board of Parole Hearings, the DA’s office called Smiley’s criminal conduct "violent and lengthy." They wrote that he committed several felony violations and had "little regard for human life and the law."The letter states that six months after his 18th birthday in 2013, Smiley was arrested and later sentenced after he was found with an assault weapon and large-capacity magazines. Later that year, he was also sentenced to two years in prison after a string of robberies, according to the DA's Office.Most recently, Smiley was serving a 10-year prison sentence after a domestic violence incident with his girlfriend. The letter to the Board of Parole Hearings from the DA's Office on April 29, 2021, asks for the denial of Smiley's release. It stated, "If he is released early, he will continue to break the law."The California Department of Corrections and Rehabilitation said Smiley went to prison in 2018 and was released on probation in February. They claim it was not an early release, saying he was awarded pre- and post-sentencing credits. | RELATED | Read the letter from the Sacramento County DA calling for Smiley Martin not to be releasedMeanwhile, detectives investigating Sunday's shooting have located hundreds of items of evidence, including more than 100 expanded shell casings and a stolen handgun that was found to have "been converted to a weapon capable of automatic gunfire," police said. In addition, lots of videos from that night have been posted to social media, including one posted before the shooting by one of the men killed, Joshua Hoye-Lucchesi.Video he shared on his Instagram account shows him with brothers Dandrae and Smiley Martin, who were arrested in connection with the shooting. The three of them were brandishing what appear to be guns, pointing them at the camera.Officer Chad Lewis with the Sacramento Police Department said, as far as the shooting investigation goes, they are still looking into how everyone is connected, as well as possible motives.Dandrae Martin's criminal history and an update on his court appearanceDandrae is being held in the Sacramento County Jail without bail and made a brief initial court appearance Tuesday at 3 p.m. He was arrested Monday on assault with a firearm and being a prohibited person in possession of a firearm charges, but the Sacramento County District Attorney's Office only read the firearm charge at Dandrae's court appearance.When asked why the assault charge wasn't presented, Chief Deputy District Attorney Rod Norgaard sent KCRA 3 this statement:“As the elected District Attorney, Anne Marie Schubert indicated this is a very complex case with a lot of evidence. As the investigation is ongoing, our ethical obligations as prosecutors prevent us from commenting on the evidence or the initial charging decisions.”Even though the district attorney only presented the one charge, police said Dandrae was arrested for the shooting, believing he fired a gun during the shooting. Officers believe there were multiple shooters, but it still remains unknown how many in total there were. Linda Parisi is the attorney representing Dandrae. She spoke with KCRA 3 outside the courthouse about the hearing."In order to properly represent someone, you have to look at all of that evidence to see what they can prove. Can they support the charges? Because as we know, Mr. Martin, as well as every person accused of a crime, is presumed to be innocent at this point," Parisi said.Asked about gun violence in the community, Parisi called it a significant issue in the community.“We need to address this," she said. "It is not just a criminal justice issue and it is narrow-sighted to say, well all we have to do is address what happened on this occasion.”She said she was assigned to the case because of overload in the public defender’s office. She said she did not know if Martin was on the scene when the shooting happened and that she did not believe he had been in contact with his brother since his arrest.Dandrae's next date in court will be April 26.| MORE | Man arrested in connection with Sacramento shooting has criminal history, court records showKCRA 3 Investigates learned Dandrae Martin has also had previous run-ins with the law.Martin has been wanted in Riverside County since 2015. Jail records show he has an outstanding warrant for a misdemeanor domestic violence charge.According to court documents, Martin “inflicted bodily injury resulting in a traumatic condition” to his spouse.Martin pleaded guilty to the charge in 2014 and was sentenced to 30 days of custody and 36 months of probation.The Riverside County District Attorney's Office confirmed to NBC News that Martin later violated two terms of probation: the community service requirement, and the 52-week class requirement.A $5,000 bench warrant was issued by the court in 2015.KCRA 3 Investigates also learned Martin spent time in an Arizona prison. He was released in 2020 after serving just over a year-and-a-half for violating probation in separate felony convictions for an attempt to commit aggravated assault in 2016, and a conviction on a marijuana charge in 2018. | MORE | What we know about the 6 people killed in downtown Sacramento mass shootingSix people were killed and 12 others were hurt by the gunfire that broke out Sunday morning in downtown Sacramento following a fight, police have said. At least seven of the people who were shot have since been released from hospitals. Lester said Monday that police now know that at least three buildings and three cars were also hit by gunfire.The coroner’s office in Sacramento County identified the three men and three women who were killed on Monday as:Johntaya Alexander, 21Melinda Davis, 57Sergio Harris, 38Joshua Hoye-Lucchesi, 32Yamile Martinez-Andrade, 21DeVazia Turner, 29Police are encouraging community members to continue submitting photos or videos related to the investigation and have shared a QR code to do so. They have received more than 170 videos and photos so far. --The Associated Press contributed to this story.