A May trial date has been set for a Minneapolis man whose 4-year-old son accidentally shot and killed his younger brother while playing with a loaded handgun stashed beneath a mattress.

Judge Daniel Moreno set Kao Chongsua Xiong’s manslaughter and child-endangerment case for a jury trial after another attempt at plea negotiations failed on Tuesday.

Xiong’s attorney, Steven Meshbesher, would not elaborate on whether offers from Assistant Hennepin County Attorney Amy Sweasy involved prison time or probation, but he described them as inadequate.

“Obviously my client feels bad about the situation, and I wanted to resolve it in a way that would accommodate that,” he said. “What specifically it was, I’m not going to discuss publicly.”

He added, however: “We were not happy with their proposal.”

In a statement, Hennepin County Attorney Mike Freeman said his office will continue attempts to reach a deal.

“We are struggling to balance the family’s grief with the tragic violation of the law that resulted in a young child’s death,” he said. “We remain hopeful that an appropriate resolution that meets that balance can be reached, and we are determined to keep working toward that goal.”

Xiong, 31, was charged with second-degree manslaughter and child endangerment, both felonies, three weeks after his 2-year-old son, Neegnco Xiong, was killed on Dec. 5. Charges say Xiong had eight guns in the two-bedroom home at 1907 7th St. S. at the time the 4-year-old was playing with the gun, which had been stashed between the bed and the mattress in his bedroom. Xiong and his wife were on the first floor of the home preparing lunch when the gun went off. They found Neegnco on the upstairs bed and his 4-year-old brother under the bed. A 5-year-old son was at kindergarten at the time, while a 1-year-old was asleep in the children’s bedroom.

Police said the safety device was missing from the loaded semi-automatic pistol used in the shooting.

Xiong, a vocational rehabilitation counselor in St. Paul, had a permit to carry the firearm, but he said he could not take the gun to work, so he tucked it into the bed.

Judge Moreno set the May 20 trial date following four court hearings that consisted largely of backdoor negotiations while Xiong and a sizable crowd of supporters waited outside the courtroom.

The trial date will be preceded by a May 13 hearing about a defense motion to suppress statements Xiong made to police after the shooting. Meshbesher wouldn’t say what the statements were but that they involved Xiong not understanding his Fifth Amendment and Sixth Amendment rights regarding making statements without an attorney present.

Meshbesher acknowledged that the jury trial could add to the trauma suffered by the family. The decision not to settle the case did not come lightly and was the result of “very deep discussions over a lengthy period of time,” he said.

“They’re going to have to relive it,” Meshbesher said. “Emotionally it’s going to be very traumatizing, but there’s no way around that. I can’t avoid that trauma.”