CHULA VISTA, Calif. – The 12-year-old boy who died over the weekend after being found with a gunshot wound is believed to have shot himself with a gun brought to his home by a friend, authorities reported Tuesday.

Chula Vista police said Maximilian “Max” Mendoza was given access to the handgun by a 15-year-old boy during a sleepover Saturday in the Woodland Hills Condominium Complex on Telegraph Canyon Road. Mendoza was said to have accidentally shot himself inside the residence before being moved outside by family members where he was found by police, according to Chula Vista police Lt. Dan Peak.

Mendoza was taken to the hospital, where he died, Peak said.

Family and friends gathered Monday night to mourn Mendoza, who was remembered as being funny, outgoing and protective of his four sisters, both older and younger.

“It’s surreal,” said Macy Mendoza, Max’s sister. “It’s like, who goes home and thinks their 12-year-old brother is gone? He was only 12, you know? So much to live for.”

The 15-year-old boy, who has not been publicly identified because he is a minor, was questioned by police. According to Peak, investigators are attempting to determine how he came into possession of the weapon and they want to determine its owner.

Legal analyst Dan Eaton told FOX 5 that under California law, if an adult believes a minor could access their gun and not secure it properly, they could face criminal charges, especially if the gun was used for serious harm or death.

“It applies whether it’s the child’s parents or not. It applies to anyone,” Eaton said. “The adult in question could be subject to imprisonment for as long as three years and a fine of up to $10,000.”

Anyone with information on potential witnesses or suspects is asked to call San Diego County Crime Stoppers at 888-580-8477.