Editors' Note: This is the first of three ABCNews.com stories featured during National Suicide Prevention Week to explore not only what motivates people to kill themselves, but to highlight those who survive suicide attempts, witness them or work to prevent them.
Ryan Thurston remembers the first time he saw a man jump to his death from the Aurora Bridge, landing in the Seattle parking lot just beneath his office window in the fall of 2005.
"It was a balmy Seattle morning, a typical morning, checking email and chatting with co-workers," said Thurston, now 35. "I had a window looking out at the bridge. I glanced down at the parking lot and saw a guy head down, blood coming from his head. He was probably 20 yards away.
"At first I thought he had tripped, then we all looked at the bridge and could see his truck with the door open," he said.
It happened again a month later and continued "on a pretty regular basis," Thurston said.
By 2006, a record nine people in one year had jumped to their deaths from the bridge, including a 15-year-old girl.
But since last year, safety barriers have been in place, thanks in large part to efforts by Thurston, who, after being so traumatized, founded Seattle Friends, a suicide-prevention organization.
"Nothing had been done, there had been no concerted effort," he said a few days before Sunday's start of the 38th annual National Suicide Prevention Week.
But Thurston had another reason to get involved: A close college friend had taken his own life. "You see the impact on family and friends," he said.
Now, state transportation officials, who spent $4.8 million on the project, say guardedly that it is working.
More than 230 people have taken their lives at the Aurora Bridge, making it the second deadliest "suicide bridge" in the United States, behind the Golden Gate Bridge, according to Seattle Friends. Since 1995, 50 people have died, and more than half of the victims landed on the pavement and busy intersections below.
Broadly speaking, a federal study shows, 8.3 million Americans -- 3.7 percent of all adults -- have serious thoughts of suicide each year; 2.3 million make a plan and 1.1 million attempt suicide, resulting in an estimated 37,000 suicide deaths each year.
Some studies show that iconic bridges and other physical structures draw those with suicidal impulses, but if barriers are in place, many deaths can be prevented.
New York University in Lower Manhattan just completed the renovation of a 150-foot-tall space after a several students jumped to their deaths inside a library.
In 2003, after two suicides less than a month apart, the university installed 8-foot, plastic-glass walls in its library's atrium. But another student scaled the wall in 2009 and killed himself. Now, a new system of lace-like aluminum panels has been installed around the balconies and staircases.
Cornell University in Ithaca, N.Y., has also addressed its suicide problem by recently installing mesh nets on five bridges that cross gorges around campus. The school has had 27 such deaths between 1990 and 2010, 15 of them students.
Some experts argue that those intent on suicide will find a way, regardless of attempts to dissuade jumpers, but one study, reported in the New York Times story, "The Urge to End It All," suggests otherwise.
Two bridges in Washington, D.C., span the 125-foot deep Rock Creek gorge, the Ellington, famous as the "suicide bridge" with about four deaths a year, and the Taft, with fewer than two a year.
But after three people died in a 10-day period in 1985, the city erected barriers at the Ellington Bridge. Critics feared jumpers would just go to the Taft instead. But five years later, a study showed no suicides at the Ellington Bridge and no change at Taft. As a result, the overall suicide deaths went down in the nation's capital by 50 percent.