Valley Springs, California (CNN) -- A 12-year-old California boy accused of stabbing his 8-year-old sister to death was charged Wednesday with second-degree murder.
Appearing in a green jumpsuit in juvenile court, he said, "Yes" when asked if he understood the charges. He didn't enter a plea.
The boy didn't appear to be nervous, shocked or stunned. He smiled while talking with his lawyer and several times he looked back at his family.
He will remain in custody while he awaits his next court appearance on May 29.
The boy's younger sister, Leila Fowler, was stabbed multiple times in her family's home in northern California on April 27 while she was there with her youngest brother.
"He's holding up well under the circumstances," one of the boy's attorneys, Mark Reichel, said Tuesday.
The boy, who was arrested Saturday, told police a man broke into the family's home.
After the killing, police described the suspect as a 6-foot-tall white or Hispanic male with a muscular build. They interviewed registered sex offenders in the area, ran down leads and searched in attics, storage sheds and more in the rural, mountainous community about 60 miles southeast of Sacramento.
On the day of the killing, Leila's father and his fiancee weren't home.
A woman called 911 and told a police dispatcher her children were scared because a strange man had broken into the house, according to an emergency call released Tuesday.
When the dispatcher asks what the emergency is, the woman tells her: "My children are home alone, and a man just ran out of my house. My older son was in the bathroom and my daughter started screaming. When he came out there was a man inside my house. I need an officer there."
The woman says that the boyfriend of an older daughter was on the phone with the children in the house.
The dispatcher asks if the children had seen the man and if they could describe him.
"They did see him, yes. My daughter is freaking out right now," she says. After giving the dispatcher a home phone number, she adds, "They said they are OK, but I need you to come."
Although the call indicates the girl was alive and well, when police arrived, they found she had been stabbed.
Leila died minutes after arriving at the hospital, authorities said. She died of shock and hemorrhages from her wounds, the Calaveras County Coroner's office said.
Before Leila's death, the boy's middle school in Valley Springs suspended him for five days after he brought a knife to school, according to one of the boy's classmates. That account was backed up by a school administration source.
Authorities haven't revealed what kind of knife was used in Leila's death.
The death of Leila, known for her bubbly personality, shook the small northern California town of Valley Springs, where ribbons in her favorite color of purple were tied to stop signs.