The business partner of a man whose remains were found along with his wife's and children's in the high desert north of Los Angeles has been arrested and charged with killing the McStay family in 2010, authorities announced Friday.

Charles Chase Merritt, 57, Joseph McStay's business partner, was arrested Wednesday in the northwestern San Fernando Valley community of Chatsworth "without incident," according to the San Bernardino County Sheriff's Department. McStay, 40, operated a custom decorative water fountain business and was working on a project with Merritt when he and his family disappeared in February 2010.

District Attorney Mike Ramos called the slayings "cold and callous" when he announced that four murder charges had been filed against Merritt, who has a criminal record, according to the sheriff's department.

Joseph McStay's brother Michael praised investigators' work at Friday's news conference, which was attended by several McStay family members.

"I just wanted to see it through to the end. Joseph was a great brother, a great father. He would have done anything to protect those boys and Summer," he said.

"He tried to provide work for Chase and help Chase," he said of his brother, adding of Merritt: "He'll get what he's got coming to him."

Susan Blake, the mother of Joseph McStay, began reading from notes at the news conference, then put them away as she spoke about her son and the call from investigators who notified her of the arrest.

"They did not deserve this," Blake said. "Joey was so generous and kind to so many people.

"I received that phone call and there's a little more to our journey. I need justice."

When asked whether the was a break in the case that cast suspicion on Merritt, investigators said there was "no smoking gun." Investigators said they reviewed evidence provided by the San Diego County Sheriff's Department that led to the arrest.

Authorities said they could not discuss a motive for the slayings. The victim and suspect met when Joseph McStay asked Merritt to create custom water fountains, investigators said.

"They started working together and became friends, that's how their relationship started," said Sgt. Chris Fisher, of the San Bernardino County Sheriff's Department.

Joseph and Summer McStay, 43, and their two young children, ages 4 and 3, mysteriously vanished from their Fallbrook home in February 2010, triggering a widespread search from San Diego County to northern Los Angeles County and a homicide investigation. The investigation revealed that the victims were killed in their home, and all were victims of blunt-force-trauma, sheriff's officials said Friday.

Fisher said Merritt is believed to have acted alone. The slayings occurred inside the McStay's home, but Fisher refused to discuss whether there was a struggle or whether a weapon was used.

More than three years after the family disappeared, skeletal remains were found in and around shallow graves in the high desert near Victorville in southwestern San Bernardino County. The location is about 100 miles north of the family's home in San Diego County.

Coroner's officials identified the remains as those of Gianni McStay, Joseph Mateo McStay and their parents. A motorcyclist reported finding the remains in a very remote location approximately 50 yards from the nearest road. Officials said it appeared the remains had been there for "an extended period of time."

What initially appeared to be one of the few possible leads in the family's mysterious disappearance also was addressed at the news conference -- a grainy surveillance video that showed four individuals resembling the McStays crossing into Mexico Feb. 8, 2010 at the San Ysidro border crossing. A white Isuzu Trooper belonging to the family was found illegally parked at a nearby strip mall the same day.

On Friday, investigators said the video does not appear to show the McStays.

"We don't believe that's them," said Fisher. "The video, once we examined that, and other evidence -- we don't believe the video was related."

The expansive search for the family was documented on a website maintained by Joseph McStay's brother, Michael. As of early Friday morning, the most recent update was in July when the family attended a private memorial ceremony for the victims.

In April 2013, the San Diego County Sheriff's Department announced they were transferring the case of the McStay family to the FBI.

Merritt said in a November 2013 interview that he was the last person to have seen McStay. Investigators said Friday that Merritt likely has not left the Southern California area for a significant period of time since the slayings.

A decision has not been made on whether prosecutors will seek the death penalty, Ramos said.

Arraignment in the case was slated for Friday afternoon, but was postponed until Wednesday, Nov. 12. It was not immediately clear whether Merritt obtained an attorney.