A scorching world record, a horrific leg break and bomb and bullet scares made for a hectic first day as the Rio Olympics swung into action on Saturday.
Vietnam and Thailand won their first ever Olympic gold medals and there was joy for teenage American markswoman Virginia Thrasher, who snared the first gold of the Games.
Elsewhere Belgium's Greg Van Avermaet won a crash-filled men's cycling road race and rugby returned to the Games after a gap of 92 years.
Britain's Adam Peaty was the early star in the swimming pool as he set an eye-popping new world record of 57.55sec in the men's 100m breaststroke heats — his first ever Olympic swim.
"Fifty-seven-five, not too shabby," shrugged Peaty, adding: "I wasn't even pumped up."
China's Sun Yang headlines the swimming finals later on Saturday when he defends his 400m freestyle title against Australia's Mack Horton.
The Rio Games started with an unwanted bang when a military bomb squad detonated a suspicious package near the finish of the men's cycle race at Copacabana beach, causing jitters among onlookers.
"The security services found a suspicious package close to the cycle road race finish line in Copacabana and as a precaution decided to perform a controlled explosion," Rio Games organisers said.
At the equestrian venue at Deodoro, which is on a military base, a stray bullet ripped through the media centre's canvas roof and landed on the floor.
"All authorities assured that the bullet was a stray bullet that has nothing to do with the Games or the Olympic family or the press. The area was not a target," said Games spokesman Mario Andrada.
America's Thrasher, 19, upset China's Du Li and Yi Siling, the 2012 gold-medallist, to win the women's 10m air rifle competition on her final shot.
'It was chaotic'
Later Hoang Xuan Vinh wrote his name in the history books when he won the men's 10m air pistol, claiming the first ever gold medal for communist Vietnam.
"It's the first gold medal in Vietnam's history, I feel very lucky," said the modest, 41-year-old military officer.
Thailand's Sopita Tanasan won the first weightlifting gold, the women's -48kg, with a total lift of 200kg in what was a strong day for Southeast Asia.
Scandal-hit Russia, under fire over a massive doping scandal, got off the mark when Beslan Mudranov won the men's 60kg judo.
Van Avermaet avoided a crash on the final descent and overhauled leader Rafal Majka with a lung-busting sprint to win the 237.5km (147.5 miles) cycle race.
"It was the hardest day I've ever had in my life on a bike," said Ireland's Dan Martin, who finished 13th, one place behind Tour de France winner Chris Froome.
"It was a brutal, brutal, strange old race."
Camille Grassineau scored the first try of the tournament — and the first ever Olympic try in rugby's sevens format — as France's women beat Spain 24-7.
Serbian rowers Milos Vasic and Nenad Bedik capsized in choppy waters at the Rodrigo de Freitas lagoon, but won a reprieve when they were allowed to move into the next round.
Zimbabwean Micheen Barbara Thornycroft said conditions were "probably the worst I've ever raced in."
"It was chaotic. It was anyone's game, whoever could get their blades in and move. I was seeing everyone catching crabs and tipping," she said.
The day's most painful moment belonged to French gymnast Samir Ait Said, whose lower left leg snapped and skewed to a horrific angle when he landed awkwardly from a vault.
Yusra Mardini, the Syrian refugee who was swimming for her life less than a year ago, won her 100m butterfly heat but failed to reach the semi-finals.
"Everything was amazing. It was the only thing I ever wanted was to compete in the Olympics," said the 18-year-old, who is representing the Games' first ever refugee team.