Four days after flash flooding devastated central Texas, dozens of people remain missing.
At least 100 people have been killed in the disaster, including schoolgirls who had been staying at a riverside summer camp.
Their deaths have devastated the local community and reignited a political debate over US President Donald Trump's cuts to the public service.
So, how did the flooding catch authorities so off guard? Here are some of the key questions being asked in the aftermath of the tragedy.
What kind of warnings did residents receive?
The National Weather Service (NWS) issued a flood watch on Thursday afternoon local time, advising of potential rainfall of up to 7 inches (17 centimetres).
But it was not until the early hours of the next morning, when many people were still asleep, that the warnings became more serious.
Alerts were being sent out to enabled mobile phones from 1:14am, with an urgent warning issued at 4:03am.
Phone reception in the affected areas can be patchy, and some residents say they did not receive the alerts.
By at least 5:20 am, some in the Kerrville City area, north-west of San Antonio, say water levels were getting alarmingly high.
Some are now calling for a siren system along the river, similar to what is used for tornadoes in other parts of the United States.
The top elected official in Kerr County, Judge Rob Kelly, says that idea was examined several years ago but considered too expensive.
"We've looked into it before … the public reeled at the cost," he told AP.
The NWS says it is "heartbroken" by the loss of life in Texas. It has released a timeline of its alerts in the lead-up to the floods and says it had conducted forecast briefings for emergency management the day before they struck.
Some meteorologists have defended its work, arguing the forecasts were as accurate as they could have been. Ultimately, they say the NWS did its job in extremely challenging circumstances.
"An overarching point that I think needs to be emphasised about this event is just what an absolute worst-case scenario it was," wrote Alan Gerard, who spent decades at the National Oceanic and Atmospheric Administration (NOAA).
"The flash flood event occurred in the middle of the night when people are typically asleep … [and] it occurred at the start of a long summer holiday weekend when campgrounds and resorts such as the ones that cluster along the Guadalupe River are most likely to be full."
Texas Governor Greg Abbott argued advance warnings of the anticipated rainfall did not reflect the scale of what was to come.
"To most people in the area, flash flooding would mean one thing, not what it turned out to be," he told reporters on Sunday, local time.
"Because they deal with flash floods all the time … but there's no expectation of a water wall of almost 30 feet [9 metres] high."
Why were summer camps in 'flash flood alley' not evacuated?
The risk of flash flooding in central Texas is well-recognised. The area's steep hills, shallow rivers and semi-arid soils mean water can move very quickly through the area, earning it the nickname "flash flood alley".
Hatim Sharif, a professor of civil and environmental engineering at the University of Texas, says it is one of the most dangerous places for flash flooding in all of the US.
This storm dumped up to 15 inches (38 centimetres) of rain in the worst-affected area, equivalent to several months of its usual annual total.
The impact on the Guadalupe River was catastrophic, with waters rising 26 feet (8 metres) in only 45 minutes.
Staff at one of the summer camps in the area, the Presbyterian Mo-Ranch Assembly, say they started moving children and staff to higher ground when they noticed the river rising.
But the nearby Camp Mystic, a Christian summer camp along the river, has been devastated. Twenty seven of the people killed in floods were campers and counsellors at the camp.
Asked why the facility was not evacuated, given its proximity to the river, Kerrville city manager Dalton Rice said it was a "great question" but that authorities were still focused on searching for those missing.
Summer camps are a long-standing American tradition during the school holidays, with Camp Mystic attracting children from across the state for nearly 100 years.
Chip Roy, a Republican congressman who represents the area, expects a debate over whether similar facilities should now be moved from vulnerable areas.
"The response is going to be, 'We've gotta move all these camps — why would you have camps down here by the water?'" the BBC quoted him as saying.
"Well, you have camps by the water because it's by the water. You have camps near the river because it's a beautiful and wonderful place to be."
Did budget cuts have an impact?
The NWS is one of many US government agencies forced to cut its staffing levels under US President Donald Trump's efficiency drives.
Tom Fahy from the National Weather Service Employees Organization told NBC that the local weather forecasting offices were adequately staffed ahead of the floods.
But he said the San Angelo office, which issued warnings for some of the affected areas, did not have a senior hydrologist or a permanent meteorologist-in-charge.
Some experts have questioned whether the vacancies could have affected the level of coordination between the NWS and local officials.
The top Democrat in the Senate, Chuck Schumer, has asked a government watchdog to investigate whether staffing vacancies in the area contributed to "delays, gaps or diminished accuracy".
"This is a national tragedy which people across the country are mourning. The American people deserve answers," he wrote.
White House press secretary Karoline Leavitt dismissed criticism of the federal response as a "depraved lie".
The president rejected concerns staffing cuts could have hampered the delivery of warnings, describing the floods as a one-in-100-year event.
"This was a thing that happened in seconds, nobody expected it, nobody saw it," Mr Trump said, adding that he did not think fired staffers needed to be re-hired.
Mr Trump did not comment on his suggestion, made earlier in his second term, that the Federal Emergency Management Agency (FEMA) should be abolished.
Could it get worse?
Texas authorities have warned the death toll is likely to rise as search-and-rescue operations continue.
Hundreds of volunteers are scouring the area around the Guadalupe River, with the chance of finding survivors diminishing with each day that passes.
Residents are also bracing for more heavy rain, which could cause further flooding across the region.
Dalton Rice, the city manager in Kerrville, said a full review would be carried out in the hope of improving the area's preparedness for future disasters.
"We owe that commitment to the families who are suffering and to every member of our community," he said.
