PORTLAND, Ore. -- Pati Gallagher remembers hearing a splash in the Willamette River several hours before daybreak, silence, and then a little girl screaming.
"At first it was, 'Help me,"' Gallagher said of the screams. "Then it went to anguishing horrible screams."
Gallagher and her husband live along the banks of the Willamette River, a wide, powerful waterway that flows through Portland.
The screams they heard apparently came from a 7-year-old girl who was either pushed or fell -- along with her 4-year-old brother -- 75 feet from a bridge over the Willamette as most people were sleeping early Saturday.
The brother and sister were found together in the Willamette. The brother died of drowning. They had floated downstream before they were pulled out of the water during a nighttime search and rescue effort.
The mother of the two children -- 31-year-old Amanda Jo Stott-Smith -- was arrested six hours later on the ninth floor of a downtown parking garage. She threatened to jump off a ledge when officers arrived, police said.
Police are not saying whether they believe Stott-Smith threw her children into the river, or whether they somehow fell. But they are holding her responsible. She faces charges of aggravated murder and aggravated attempted murder at her arraignment Tuesday.
Police have not given a possible motive. "There's some psychological issues, obviously," said Sgt. Mike Marshman, a Portland Police Bureau spokesman. "There has to be...Just look at the facts."
The mother has a history of domestic violence and recently filed for separation from the children's father, according to court documents.
What happened early Saturday has unsettled residents who live along the Willamette as well as police who responded and heard the screams.
Pati and Dan Gallagher, both 50, live in a town home near the Sellwood Bridge. They were sitting on their patio, they said, when they heard a splash, and then screams.
Pati Gallagher called 9-1-1, while her husband and a woman out on a river trail yelled out, asking the girl to tell them her location.
The operator on the other line could hear the girl, said Gallagher, who made three emergency calls by the time the incident ended.
When police and rescue workers arrived, they also heard the screams but were unable to locate the source.
The couple said the splash seem to have occurred near the river's west bank, about a third of a mile from their home.
The brother and sister began to float downstream, the girl yelling for help.
By 2:10 a.m., police said, the children were pulled from the water and taken to authorities near the Oregon Yacht Club by an unidentified couple who joined the search in their boat.
"It's tough to get the sounds out of my head -- the screaming, the splash," Dan Gallagher said.
A state medical examiner determined that Stott-Smith's son, Eldon Jay Rebhan Smith, drowned. Her daughter, who has yet to be identified, was taken to an area hospital after surviving more than a half-hour in the water.
Police said Sunday afternoon that the girl's condition was improving and she had spoken with officers.
"How she's not dead is a miracle," said Sgt. Marshman, who has witnessed people take their lives by jumping off the bridge south of downtown.
Stott-Smith filed for separation from her husband, Jason Smith, in March, according to Washington County Circuit Court records. The parents had joint custody of the children, Marshman said.
Court records show Stott-Smith had been charged with domestic assault in 2000.
Early Saturday, the father filed a missing persons report in suburban Tualatin that helped authorities identify the children, said Sgt. Detective Rich Austria.
There was no answer at a telephone number associated with Jason Smith on Sunday.
Police are in awe of the girl, whom Marshman describes as "tiny for a 7-year-old," and of how she was able to survive the long fall and withstand more than 30 minutes in the cold Willamette.