A teenage son of a wealthy couple shot to death in their San Juan Capistrano home is accused of killing them while they slept last month.

Authorities said the attack on Feb. 9 paralyzed the teen’s younger brother and included an attempt to kill one of his sisters.

The arrest of 19-year-old Ashton Colby Sachs on Friday ended a weeks-long investigation that had puzzled detectives, who say they still are trying to determine why the teen targeted his family.

“We’re still working to find a motive,” said Justin Montano, the Orange County Sheriff’s Department detective leading the case. “We’re looking at all the angles right now.”

Sachs is charged with two counts of murder and two counts of attempted murder. Prosecutors did not say if they’ll seek the death penalty.

Investigators found no signs of a break in at the home in the 32200 block of Peppertree Bend, a cul-de-sac lined with mansions in one of San Juan Capistrano’s most exclusive areas.

Police believe Sachs traveled to Orange County from his home in Seattle, where he and his older brother, Myles, were involved in business ventures also linked to his parents, Bradford Hans Sachs, 57, and Andra Sachs, 54.

The suspect entered the home armed with a gun and shot his parents in their bedroom, then went to his 8-year-old brother’s room and shot him, according to the District Attorney’s Office. He then fired at his 17-year-old sister, missing, before fleeing the home and returning to Seattle, authorities allege.

One of the couple’s two daughters – police haven’t identified her – called deputies just before 2 a.m. to report the gunfire. Investigators interviewed Ashton Sachs and other members of the family soon after the shootings, but they “initially found little evidence leading to a suspect,” Sheriff Sandra Hutchens said.

A lead earlier this week led them back to Ashton, but investigators declined to reveal more. Detectives interviewed Ashton on Thursday in San Diego County, where he and his siblings planned to live, and then arrested him.

Law enforcement personnel also returned to the San Juan Capistrano house with a search warrant and seized several documents and computers.

“We feel confident he’s our suspect,” Montano said. “Right now, we believe he’s our only suspect

Ashton Sachs appears to have no criminal history beyond speeding tickets in Orange County and Washington state.

He is the second-oldest of the Sachs’ five children, two of whom were adopted. He and his older brother, Myles, filed court papers two weeks after the shootings asking to be named guardians of their younger siblings, including the injured boy. The court records show that they also sought guardianship of the family’s estate.

Ashton graduated from Dana Hills High School, then attended Saddleback College for two years where he was enrolled as a computer-science major. More recently, he was attending school in the Seattle area, where his brother Myles also goes to school. A traffic ticket he received in November lists an address in Gig Harbor, south of Seattle.

As a high-school student, Ashton stood out in computer-programming classes and had a talent for creating smart-phone apps, according to Paul McManus, his former teacher at South County’s regional occupational program. “He’s a great kid, exemplary,” McManus said Friday.

“He seemed like he really enjoyed his parents,” McManus said. “Dad sounded like a really interesting guy. He raved about him.”

A blogger who used the name Ashton51 wrote a 2013 tribute to Andra Sachs, praising her as an “entrepreneur and leader” with the experience to help other businesses. “You can make lots of money… but the most difficult task is to keep it,” the post cautioned.

The killing of the Sachs inside their 8,700-square-foot home – described by one real-estate broker as a fortress – initially left investigators with few clues. Officials with the Orange County Sheriff’s Department said there was no sign of forced entry in the $3.7 million house on a quiet cul-de-sac.

Montano described the case as a “true who-dunnit, since the beginning.” He said detectives interviewed friends, family members, past business associates and “a long list of people… that may not have liked the family.”

The killings shocked San Juan Capistrano residents and dominated town gossip for days, but discussion tapered as the investigation proceeded with little news, said Joel Barrett, bartender at Swallow’s Inn.

Still, the case remained on the minds of many. “The community cares. That’s the bottom line,” said Kimberly Bennink.

Records show that Bradford and Andra Sachs helped launch a series of tech and green companies and owned properties in California, Florida, Nevada and Mexico. They also had a trail of court cases filed against them and their businesses.

The couple filed for divorce in 1999, a process that was so bitter that one judge said he wanted to make sure they stayed away from each other. They remained divorced – a financial decision, according to one friend – but soon resumed doing business and living together. The friend, Monte Burghardt, described them as soul mates.

On Friday, their son Ashton was being held without bail at the Orange County Jail. The District Attorney’s Office said it had filed charges against him of murder and attempted murder with premeditation and deliberation..

Register staff writer Scott Schwebke and Ericka contributed to this report.

Contact the writer: 714-704-3788 or shernandez@ocregister.com