Of course only in San Francisco. According to the Cronicle: A Walnut Creek woman who killed her teenage son on Mount Diablo before shooting herself was angry that the boy was spending more time with her ex-husband, her brother told The Chronicle after reading her suicide note.

Judith Elizabeth Williams, 51, decided to kill her 16-year-old son, Adam Williams, in part because her ex-husband had recently moved back to California from Missouri and was spending every other weekend with their son, her brother said. On Friday, father and son were to have left on a trip to Southern California.

“She didn’t want Adam to go to his dad,” Williams’ brother, Bill Collins, 55, of Palo Cedro (Shasta County) said Friday. “That was obvious.”

On the afternoon of July 17, Williams and Adam drove up to Lookout Point near the top of Mount Diablo. They got out of her Toyota Corolla and enjoyed the view. Williams took a picture of her son and then ambushed him with two shots to his chest and head before killing herself, authorities said.

“I loved my sister,” Collins said. “I have to have sympathy for her plight, but I have no sympathy for her taking Adam. Since she shot that beautiful boy, that sympathy goes out the window.”

Collins said his sister had made clear in a three-page, typed suicide note found beside her computer that she wanted her and her son’s lives to end.

She described taking her cats to a shelter the day before and of taking Zachary, the family dog, to the veterinarian to have it euthanized at 11:45 a.m., only hours before the drive up to Mount Diablo, Collins said.

She expressed anguish that Adam, the boy she had raised alone since she filed for divorce from Jim Williams in 1996, was spending more time with her ex-husband, Collins said.

“It seemed extremely calculating and deliberate in its purpose,” Collins said of his sister’s reasoning.

He said his sister had also touched on financial problems she had been having for at least a decade. She wrote something to the effect of, “This was (the) only option because bills are due,” Collins said.

Judith Williams filed for bankruptcy protection once, in 1999, and her landlord told The Chronicle that she was behind on the $1,700 monthly rent for her house on Blackwood Drive.

After their five-year marriage dissolved, Jim Williams moved to St. Louis and saw his son only during the holidays. Her former husband, now 45, moved to Roseville (Placer County) a couple of years ago and started seeing Adam every other weekend and a couple of weeks each summer.

“I thought it was the right thing to do,” Collins said.

But Judith Williams was “livid,” her brother said. She felt that she had done all the work of raising Adam.

“She had a chip on her shoulder that I never really understood,” Collins said. “It was kind of strange.”

Collins said his sister could be difficult and was “tough as nails” in her dealings with others. She had a falling-out with their younger brother and had only recently made up with her older sister after a dispute, Collins said.

“There was a difficult family dynamic,” he said.

Despite their problems, he said, the siblings had reached out to Williams, offering her money and support. Collins said he had encouraged his sister and Adam to come live with him in Shasta County.

Why Williams took the path she did will forever haunt her family, Collins said.

“I wouldn’t say I’m angry. I would say I’m ashamed,” he said. “I’m bewildered. I’m perplexed. I’m sad she would do something like that” to a son she treated “like solid gold.”

Dax Harris, head track coach at Las Lomas High School in Walnut Creek, where Adam would have been a junior in the fall, said the boy had been “improving every day” on the field.

“It’s a really tragic circumstance. I think it’s kind of a selfish act,” Harris said Friday as he prepared to attend a memorial for Adam in Fair Oaks (Sacramento County).

“I really don’t see the point in something like this,” Harris said. “I figure you can set differences aside when it comes to divorce and doing stuff with the kids.”