A 35-year-old Healdsburg mother who left her two children unattended in her locked minivan in her driveway for about eight hours -- causing the death of her 2-year-old son -- is on suicide watch at the Sonoma County jail.

The woman, Rena Corban, 35, told the Healdsburg police that she had taken five times the prescribed amount of the painkiller Vicodin for a flareup of an old back injury. Three empty wine bottles also were found in her blue 2004 Toyota Sienna minivan, which has been impounded, said Healdsburg Police Sgt. Tony Pinochi.

The boys' father, Justin Paulsen, 39, called 911 at 6:10 p.m. on Thursday after he returned home from his job at a Healdsburg winery and discovered his wife intoxicated on the couch and unresponsive.

Paulsen pulled 2-year-old Liam's pale body from the minivan where he lay strapped in his child safety seat -- and started CPR on the front lawn of their gray split-level home on the 200 block of Hummingbird Court.

Healdsburg Police Chief Susan Jones estimated the temperature inside the van at 120 degrees. "No one could survive that,'' she said.

Paulsen's 4-year-old son, whose name was not released, was lying naked on the van's floorboards below the front seat. With the van's dark-tinted windows closed and the child-safety locks activated, he had been trapped there, unable to summon help.

Liam was pronounced dead in the ambulance en route to the Healdsburg District Hospital.

The older boy was treated by emergency personnel at the scene and released to his grandmother. He is now back with his father.

Corban told Healdsburg firefighters who treated her Thursday night that she was thoroughly distraught and was going to kill herself. She is being held without bail, and when she appears in court Monday, she may be charged with homicide.

On Thursday morning, Corban told the police, she had told her bosses at a Santa Rosa engineering firm that her older boy was sick. After running an errand with her sons, she parked the van about 10 a.m. about halfway up her driveway, partially in the shade of a bush.

She then went inside the house, leaving her kids stranded inside the van.

It wasn't her first brush with child endangerment.

On Oct. 9, a Santa Rosa police officer waited 20 minutes outside Corban's locked car, where Liam had been left unattended with the windows closed. The officer gave her "a stern warning'' and documented the case but didn't issue a written citation when Corban appeared to be sober and said she just had gone briefly into a jewelry show at the Santa Rosa Fairgrounds, Pinochi said.

On Friday, a man answering the doorbell at the house said the Paulsen family was refusing interviews. The curtains in the front room were drawn shut. The front door is decorated with a "Home Sweet Home" ornament with seagulls.

Police said the couple had fought about Corban's drinking in the past. They filed for divorce in October 2003 but chose to stay together.

Two months later, Corban summoned the police to the house on Dec. 3 and 14 -- at 6:35 p.m. both days -- after her husband had returned from work and verbal arguments had become especially heated.

In the second incident, officers reported that the couple had an argument over Corban's drinking.

Justin Paulsen was not physically abusive nor did he threaten physical violence in either incident, police said.

On Friday, the neighbors were shocked by the incident.

Across the cul-de-sac, Yaqui Lara said he arrived home at 3:30 p.m. on Thursday and was working in his backyard when he heard a car alarm go off for about 40 seconds.

"It is so disturbing. I was so close, and if I had just gone to investigate, maybe I could have seen inside,'' said Lara, a former firefighter. "It is hard to bring a child back."

Lara said Corban, who had a quiet demeanor, always struck him as conscientious. Paulsen was often seen taking one of the kids out in a jogging stroller or playing with the kids on their bicycles in the driveway.

"I knew there was some trouble between the couple, but it didn't seem to interfere with their ability to be good parents,'' Lara said.

Three neighbors told detectives that they heard the car alarm, but no one investigated the cause. Pinochi wasn't sure whether the boys could sound the alarm from inside the van.

"That's the problem with car alarms. You hear them all the time, and no one responds to them,'' he said. "It would have been a good idea in this case. ''

A friend visiting the Paulsen family, who declined to be named, said the parents "are really upset. They aren't bickering about who is to blame. They are just dealing with their loss,'' he said.

Pinochi said a pathologist at the Sonoma County coroner's office could not determine the exact time of death in a Friday autopsy. The pathologist's preliminary cause of death for Liam Paulsen was heat exposure, pending the results of toxicology tests.

Pinochi that Corban had no recollection of what she had done to her children. A blood sample was taken to test Corban's alcohol level. She is scheduled to be arraigned in Sonoma County Superior Court at 8:30 a.m. Monday.

"She was confused, despondent and upset. She was aghast at what she had done to her family, but she had no recollection of what happened,'' he said. "When she found out that her son was dead, she acted surprised and upset.''

Last year, 42 children under age 14 died of hyperthermia inside of cars, said Janette Fennell, founder of Kids 'N Cars, a Kansas-based nonprofit group that advocates public education and legislation to prevent children from needlessly dying in vehicles.

"Young children heat up three to five times faster than adults," she said. "Their regulatory system is immature and cannot dissipate heat sufficiently. ''

A 2002 California law imposes a $100 fine on anyone cited for leaving a child unattended in a car, she said.