A man who murdered five family members then shot himself to death left the haunting lyrics of a Grammy-winning song next to his computer and a note that read, "Woe is me. I'm looking forward to seeing you in the next life," the sheriff said Wednesday.

Investigators are still baffled about why David McGowan (search), a 44-year-old investigator for the district attorney's office, killed his wife, mother and three children early Tuesday while they slept.

"This investigation is not complete. We're trying to figure out why this very tragic situation occurred," Sheriff Bob Doyle (search) said. "What was troubling this young man that he would do such a tragic thing?"

Investigators searching McGowan's sprawling, two-story ranch home in rural Riverside County (search) found the typed lyrics of the Los Lonely Boys song "Heaven" next to his computer. The song is about being trapped and lost in life, and McGowan's note was on the same sheet of paper as the lyrics.

Based on a trail of bloody sock prints, investigators determined that McGowan used his duty weapon to kill his wife Karen, 42, and mother Angelia, 75, upstairs then went downstairs and killed the children — son Chase, 14, and daughters Paige, 10, and Rayne, 8.

Each victim was shot once in the head, except for his wife, who was shot twice, Doyle said. David McGowan was found near the front door, with a phone and gun nearby.

Deputies were sent to the ranch after someone from the house — likely David McGowan — called 911 at 4:33 a.m. Tuesday. The call begins with the sharp crack of an apparent gunshot and ends with rustling and several loud thumps — apparently McGowan and the telephone falling to the floor.

No words were spoken during the brief call.

Colleagues said McGowan, who helped prosecutors prepare cases for trial, gave no clues that anything was wrong.

A model employee, he had just returned from a week's vacation and had received an outstanding review, said Ingrid Wyatt, a spokeswoman for the district attorney's office. He had a normal workload, she said.

"He reported to work every day, just like normal. We weren't aware of any financial or personal problems within the family," she said. "That's why we're all so shocked about the situation."

Friends and neighbors said McGowans appeared to be a happy couple and were loving and attentive to their children. The two met while McGowan was working as a detective at the Cathedral City Police Department near Palm Springs and his wife-to-be was the city's only female firefighter.

"Dave was a great guy. He was so quiet and humble. He was all business, very professional," Cathedral City Fire Chief Steve Sowles said.

Sowles said he ran into David McGowan a few weeks ago at the courthouse and noted that he seemed to have aged a lot in the six months since they last met. He said he attributed it to the stress of the investigator's job.

"I was surprised (by) how gray his hair had gotten and he looked tired," Sowles said. "I thought to myself, 'Gosh, we're getting old."'

Karen McGowan quit her job about nine years ago to be a stay-at-home mom, former colleagues said. She operated a small tree-trimming operation called Sawbucks from the couple's ranch home in the San Jacinto Mountains.

Neighbors often saw the children playing outside the house on a trampoline or riding bikes.