A Sylmar man described by police as a “serial killer” was charged with murder and attempted murder Tuesday and is believed to be responsible for five days of shootings that killed four people and wounded several others, authorities said.

LAPD officials said they recovered a shotgun with a pistol grip from the home of Alexander Hernandez that connects him to three separate shootings in the San Fernando Valley on Sunday in which three people were killed.

Hernandez, 34, was charged Tuesday with killing a man who was found Thursday slumped over the wheel of his truck at a Pacoima intersection and with a shooting the next day in West Hollywood involving a couple who were uninjured.

“Nothing makes a homicide investigator’s heart beat faster than realizing he has a serial killer. And that is what this man was,” Sheriff’s Chief Bill McSweeney said. “This man is and was a serial killer....I don’t think we will ever have an adequate explanation for these terrible murders. How do you explain anything like this?”

LAPD officials said they expect additional charges to be filed soon against Hernandez in connection with the San Fernando Valley shootings and another incident last week in which a motorist was shot and seriously wounded by a shotgun as she got off the 5 Freeway in Atwater Village.

“We’re very confident of that,” said Deputy Chief Kirk Albanese, who heads the LAPD’s detective bureau. “We believe we have the right man.”

Hernandez also was charged with animal cruelty in the Saturday shooting of three dogs in Pacoima. Two of the dogs were killed; the third was wounded.

LAPD officials said they believe Hernandez acted alone and was randomly shooting people on local streets and freeways.

Albanese said that he did not know the motive and that Hernandez had been uncooperative with detectives since his arrest Sunday by SWAT officers who took him into custody at his home on Kismet Avenue.

Police said the shootings followed a similar pattern, involving a lone man firing a shotgun from a tan  or gold sport utility vehicle from close range.

“He inflicted horrific injuries,” Albanese said.

Hernandez failed to appear at his scheduled arraignment Tuesday afternoon. A sheriff’s detective said he refused to leave his jail cell, prompting a judge to issue a warrant for him to appear in court Wednesday.

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