Montebello man convicted in 2010 triple slaying in Hawaiian Gardens

A jury on Nov. 12 found a Montebello man guilty of three counts of first-degree murder in a 2010 case in Hawaiian Gardens, according to the Los Angeles County District Attorney’s office.

Joseph Mercado, a 31-year-old Latino man, was found guilty in the deaths of Serena Tarin, his ex-girlfriend and the mother of his infant son; Alfred Tarin, Serena Tarin's brother; and Alfredo Tarin, their father.

The prosecutors said Mercado entered the Tarin home in Hawaiian Gardens at 3:30 a.m. on May 6, 2003. He went in through a back entrance and began firing an AK-47 rifle, according to Los Angeles County sheriff’s deputies.

Mercado then went upstairs where he shot Serena Tarin, 23, and Alfred Tarin, 19, deputies said. They were both in their beds. Alfredo Tarin, 54, was taken to the hospital and died later in the day, according to coroner's records. Two other people were wounded.

Authorities said that Mercado was upset after breaking up with Serena Tarin and that he shot the family members and then attempted to burn the home by dousing it with gasoline.

Some family members escaped by climbing onto the roof from a window, sheriff's Lt. Don Slawson said.

A sheriff’s deputy was in the area when he heard gunfire about 4 a.m. and went to the home. When he ordered Mercado to drop his weapon, Mercado turned toward the officer. The deputy fired two rounds, one of which grazed Mercado's head. The deputy then arrested Mercado.

Jurors also found Mercado guilty of three counts of attempted murder, as well as one count each of first-degree burglary, shooting at an inhabited dwelling, arson of an inhabited structure and child abuse. Jurors found true special-circumstances allegations of multiple murders, lying in wait and engaging in arson. Additionally, jurors found true allegations that the defendant personally inflicted great bodily injury and intentionally discharged a firearm during the crime.

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