AP Photo/Los Angeles Daily News, Dean Musgrove

Los Angeles Police Department officers investigate the scene of a shooting Sunday, Aug. 24, 2014, where one person was killed near the 14400 block of Polk Street in Sylmar, Calif.

By Tami Abdollah, Associated Press

Published Tuesday, Aug. 26, 2014 | 4:07 p.m.

Updated 57 minutes ago

LOS ANGELES — A man in custody is a serial killer who is suspected of randomly shooting seven people, leaving four dead, over five days in the Los Angeles area, authorities said Tuesday.

Deputy Chief Kirk Albanese said at a news conference that the three other victims were critically injured and two dogs were also shot and killed before the arrest of 34-year-old Alexander Hernandez of Sylmar.

Los Angeles police SWAT officers took Hernandez into custody Sunday evening with a pistol-grip shotgun in his possession that they believe was used in the attacks.

Prosecutors have charged Hernandez with one count of capital murder, two counts of attempted murder and three counts of animal cruelty. He's scheduled to be arraigned Wednesday and remains held on $1 million bail.

Prosecutors didn't know if he had retained an attorney. Albanese said Hernandez was being uncooperative with police.

The shootings began on early Aug. 20 when a woman was shot and wounded by a lone man in an SUV as she exited a freeway. The other shootings occurred over four straight days leading to the killing of three people on Sunday.

Hernandez has only been charged in one of the killings. Still, Los Angeles County sheriff's Chief of Detectives Bill McSweeney said he "is and was a serial killer."

The charges against Hernandez carry a potential death penalty, and prosecutors will ask that he be held without bail.

Authorities said the shootings appeared random and there was no known link between the victims or motives. Authorities requested the public's help in filling in details on the shootings.

Police believe Hernandez worked alone and is the sole suspect in Sunday's shootings. Detectives pieced together the incidents because of the timing, weapon used and descriptions of the vehicle, McSweeney said. Investigators will be reviewing unsolved shootings dating back several years, that involve similar descriptions of a tan or gold SUV and shotgun.

The Los Angeles Police Department and Los Angeles County Sheriff's Department created a 70-person taskforce along with San Fernando police to investigate the shootings, examining surveillance video among other measures.

Hernandez was charged with murder in the shooting of 48-year-old Gildardo Morales as he drove his pickup truck to work on Aug. 21 in Pacoima. He's accused of firing at a couple in their vehicle in West Hollywood on Aug. 20, and shooting three dogs, killing two, on Aug. 20.

Police say Hernandez killed three people within an hour on Sunday. He has not been charged in those deaths, but Albanese said investigators are confident they have the man who did it in custody and the public is no longer at risk.

Hernandez has served prison time and has four prior convictions, including possession for sale of methamphetamine, possession of a controlled substance with a firearm, and possession of a firearm by a felon, authorities said.