Man Killed Girlfriend's 8-Year-Old Son Because He Might Have Been Gay: Prosecutor

Isauro Aguirre allegedly tortured and killed Gabriel Fernandez.

A California man on trial for allegedly murdering his girlfriend's young son is accused of carrying out the crime because the thought the boy was gay.

Isauro Aguirre, 32, is also accused of torturing 8-year-old Gabriel Fernandez prior to his death. A Los Angeles County District Attorney's Office prosecutor asserted the alleged motive during opening statements.

Read: Man Arrested for Allegedly 'Marrying' Stepdaughter at Age 12, Holding Her Captive for 19 Years

"The evidence will show that the defendant is nothing more than a bully," prosecutor Jon Hatami said Monday. "He was a security guard who intentionally tortured and abused a helpless and innocent little boy.”

Gabriel was hospitalized and died two days later. Both Aguirre and Gabriel's mother, Pearl Fernandez, are charged in his slaying. 

Prosecutors allege Fernandez and Aguirre conspired to kill the boy then cover up his murder. 

Fernandez is awaiting trial.

Aguirre's attorney is not refuting allegations that his client killed Gabriel but he said his client should not receive the death penalty because he did not torture the boy.

He said his client actually flew into a rage after Gabriel told his mom to leave him.

Hatami argued Gabriel was bitten, burned him with cigarettes, whipped, shot with a B.B. gun, starved, fed cat litter, and kept gagged and bound before succumbing to his injuries in May 2013.

“Eight months of torture and abuse of Gabriel Fernandez by Pearl Fernandez and Isauro Aguirre in Palmdale,” the prosecutor wrote before the start of the trial, according to CBS Los Angeles.

Read: Man Arrested for Sexually Assaulting 2-Year-Old Girl in Chick-fil-A Bathroom

Hatami added that the boy was “withheld from school by the defendants for the last three weeks before he was murdered.”

Aguirre's attorney argued his client never meant for Gabriel to die. His trial is expected to last eight weeks.

Watch: Stranger Rescues Toddler Wandering Busy Road, Takes Him to Parents at a Bar