2nd arrest made in downtown Sacramento shooting that killed 6

A second suspect has been arrested in connection with a shooting that killed six people in a popular nightlife area in Sacramento, California, Sunday.

Smiley Martin, 27, was taken into custody Tuesday, Sacramento police said in a statement.

Martin has been receiving medical treatment for "serious injuries" from gunfire and is under police supervision in a hospital, police said. He will be booked once his care is complete and is being charged with possession of a firearm by a prohibited person and possession of a machine gun.

He was recently released from prison on probation in February, according to Martin's criminal records. Throughout his adult life, Martin has "displayed a pattern of criminal behavior," and has previously been convicted of felonies such as robbery and possession of a firearm, according to a letter, obtained by ABC News, that the Sacramento County District Attorney's Office sent to the state's parole board in 2021, requesting that Martin be denied early release.

Smiley Martin's brother, Dandrae Martin, 26, was identified as a "related suspect" in the shooting, which broke out on K Street in downtown Sacramento early Sunday morning just after a fight took place, the Sacramento Police Department said. Martin was arrested on assault and illegal firearm possession charges on Monday, police said.

A third person was arrested on illegal firearm possession charges, but authorities have since determined that the type of firearm recovered was not used in the shooting.

More than 100 shell casings were recovered from the scene, according to police. Investigators are sifting through hundreds of pieces of evidence, Sacramento Police Chief Kathy Lester said during a press conference Sunday afternoon.

Video posted on Twitter on Sunday showed people running through the street as the apparent sound of rapid gunfire could be heard in the background.

The victims were identified by the Sacramento County Coroner’s office on Monday as Johntaya Alexander, 21; Melinda Davis, 57; Sergio Harris, 38; Joshua Hoye-Lucchesi, 32; Yamile Martinez-Andrade, 21; and Devazia Turner, 29.

At least a dozen people were injured in the shooting, Lester said. The conditions of the injured victims were not immediately known, police said.

Sacramento Mayor Darrell Steinberg condemned the shooting during a news conference Sunday afternoon, describing it as "a senseless and unacceptable tragedy."

"And I emphasize the word unacceptable," Steinberg said. "Thoughts and prayers are not nearly enough. We must do more as a city as a state and as a nation.

ABC News' Bill Hutchinson, Zohreen Shah, Alex Stone and Jennifer Watts contributed to this report.