Todd Bachman, father of a 2004 Olympian, died in the attack. His wife, Barbara, suffered multiple stab wounds. She has undergone eight hours of surgery and remains hospitalized in critical but stable condition.
The Bachmans are the parents of 2004 volleyball Olympian Elisabeth "Wiz" Bachman and the in-laws of U.S. men's volleyball coach Hugh McCutcheon. The attack came hours after the Olympic games' spectacular opening ceremony. A Chinese tour guide was also wounded.
China's official news agency says the attacker jumped off a balcony to his death. The 47-year-old had gone through a second divorce in 2006 and reportedly became despondent after his son began getting into trouble with the law.
The Bachman were attacked while visiting the 13th-century Drum Tower on Saturday.
Police tightened security Sunday as they investigated the fatal stabbing, an attack that stunned the athletic community and embarrassed Chinese authorities determined to hold the most successful Summer Games ever.
The U.S. men's indoor volleyball team played for the first time on Sunday, reports CBS News correspondent Jeff Glor, defeating Venezuela even as they were forced to deal with a tragedy that's shaken their team.
Rob Browning, leader of the men's volleyball team, said the team was united in supporting the Bachmans.
"We are absolutely devastated by what has occurred, for their loss and for everything they are going through," Browning said. "We are a family, and we'll get through this together as a family."
U.S. President George W. Bush, in the Chinese capital to attend some Olympic events and meet with Chinese leaders, thanked President Hu Jintao on Sunday for his government's handling of the attack.
"Your government has been very attentive, very sympathetic, and I appreciate that a lot," Bush said.
Hu said his government took the incident "very seriously" and pledged to keep Washington apprised of the investigation.
Elisabeth Bachman was with her parents at the time of the attack, but was uninjured. Her father was chief executive officer for Bachman's, Inc., a home-and-garden center based in Minneapolis.
Shortly after the attack, the assailant, Tang Yongming, 47, leapt to his death from a balcony on the Drum Tower, just five miles (eight kilometers) from the main Olympics site, the official Xinhua News Agency reported.
Built in the 13th century, the Drum Tower is one of the few ancient structures in fast-developing Beijing. Drummers pounded their massive instruments on the hour to let people in the imperial city know the time.
It was closed to tourists Sunday, a note at the ticket booth asking for visitors' understanding. Someone had left a bouquet of yellow and white lilies and chrysanthemums at the entrance, flowers of mourning in China.
The midday attack Saturday sent shock waves through the games precinct after the Olympics' spectacular opening ceremony had set an ebullient tone.
There was no indication that the assailant knew that his victims had any connection to the games, according to Olympic and Chinese authorities.
Violent crime against foreigners is rare in tightly controlled China, and the assault occurred despite major security measures that have blanketed the capital city during the Olympics. A 100,000-strong security force plus countless volunteer guards have been deployed to protect against any trouble.
Wang Wei, vice president of the Beijing Olympic organizing committee, said Sunday that security in and around the Olympic venues was already sufficient but would be increased at scenic spots around the city.
He said Chinese investigators and U.S. Embassy officials believe Saturday's attack was "an isolated incident" and suggested that such random acts are difficult to prevent.
"Beijing is a safe city, but unfortunately we are not immune to violent acts," Wang said at daily media briefing.
Interpol said initial investigations found nothing indicating the murder was linked to terrorism or organized crime.
An initial investigation showed that Tang had no job in Hangzhou when he came to Beijing on Aug. 1, a spokesman with the Beijing Municipal Public Security Bureau told Xinhua. Zhejiang police said Tang had worked for a factory in Hangzhou, but had resigned, Xinhua said.
He and his wife divorced in 2006. He sold his apartment the same year and had lived in a rented house since then.
"Tang has no criminal record. His neighbors said they hadn't seen any abnormal behavior from him before he left Hangzhou," Xinhua quoted a spokesman for the Zhejiang Provincial Public Security Bureau as saying. His name was not used, as is customary.
U.S. Ambassador Clark T. Randt visited the victims in the hospital, and the embassy issued a statement later that said the attack "appears to be a senseless act of violence."