Hurricane Harvey continued to pound southeastern Texas on Sunday with “catastrophic flooding” in Houston, forcing residents to move to higher ground as officials continue to respond to thousands of 911 calls for rescues. More than 1,000 people were rescued overnight Sunday, with more than 2,000 calls to 911 for rescues pouring in, Houston Mayor Sylvester Turner said in a news conference Sunday. Turner assured priority has been given to life-threatening calls and defended his previous decision not to ask residents to evacuate before the heavy rain swamped roads. “If you think the situation right now is bad and you give an order to evacuate, you are creating a nightmare,” Turner said. The director of the Federal Emergency Management Agency, Brock Long, said the government is expected to conduct a “mass care mission” and predicted that the aftermath of the storm would require FEMA’s involvement for years. “This disaster’s going to be a landmark event,” Long said. Texas Gov. Greg Abbott told “Fox News Sunday” the storm is “bad news growing worse.” “We’re measuring rain these days not in inches but in feet,” Texas Gov. Greg Abbott told “Fox News Sunday.” Houston Police Chief Art Acevedo echoed Abbott’s concerns on “Fox and Friends Weekend,” saying the city’s 911 system has been “overwhelmed” since Harvey struck. “Do not call 911 unless it is a life or death situation…[we’re telling people] not to panic,” Acevedo said, adding that “we haven’t seen the worst of it yet.” Acevedo also urged residents not to go to their attics and instead seek refuge in their roofs. “Reports of people getting into attic to escape floodwater — do not do so unless you have an ax or means to break through onto your roof,” Acevedo wrote on Twitter.

The National Weather Service issued a flash flood warning in parts of southeastern Texas and a tornado warning in Harris County until 11 a.m. local time. At least one person died due to the flooding, Houston Fire Department’s Sheldra Brigham said. Paramedics found the individual in a vehicle just before 10 p.m. A doctor, a passerby who stopped to help, was already at the scene and pronounced the person dead. The hurricane dumped more than 20 inches of rain in the Houston area, causing “life-threatening catastrophic flooding” in southeastern Texas, The National Hurricane Center reported. Up to 40 inches of rain is expected in some parts. Harris County sheriff’s spokesman Jason Spencer said flooding throughout the county that includes Houston and the region is so widespread that it’s “difficult to pinpoint the worst area.” “It’s heartbreaking,” Spencer said. Acevedo said rainwater threatens to bring more flooding into the city in the coming days as it trickles down from other parts of the state. “[I] cannot emphasize enough how much flooding there is on roadways. You are endangering yourself and our first responders by being out. Stay put,” Acevedo wrote on Twitter earlier. Meanwhile, Harris County Sheriff Ed Gonzalez and Turner continued urging residents on Twitter to “shelter in place” and stay off rain-swollen roadways.Gonzalez actively used Twitter overnight Sunday to field assistance for those trapped inside water-soaked homes, attics and vehicles. Those appealing for assistance or being steered to help via Gonzalez’s Twitter feed included a person suffering “cardiac-arrest,” and a woman who posted: “I have 2 children with me and the water is swallowing us up. Please send help.” Gonzalez at one point appealed for calm and patience, saying officials were “trying to make it to everyone as best we can.”

The airfield was closed at William P. Hobby Airport Saturday night due to standing water on the runways, according to FOX26. Hundreds of flights were canceled and travelers were left stranded in the area. Harvey made landfall as a Category 4 hurricane late Friday night, but downgraded to a tropical storm by Saturday. The hurricane center said in its 4 a.m. Sunday update that the tropical storm has maximum sustained winds of 45 mph and remains stationary about 45 miles northwest of Victoria, Texas. A second person was confirmed dead in a house fire as the hurricane came ashore Friday night. Aransas County Judge C.H. “Burt” Mills Jr. told the Austin American-Statesman that 12 to 14 other people were injured. Trump announced on Sunday he will be heading to Texas as soon as possible and praised emergency crews and government officials for search and rescue efforts. “I will be going to Texas as soon as that trip can be made without causing disruption. The focus must be life and safety,” Trump tweeted. New York City Mayor Bill de Blasio also said on Twitter the city will be sending 120 emergency personnel to Texas to assist with the storm’s aftermath. The Red Cross opened 21 shelters to hold about 1,450 people. The Coast Guard, which received more than 300 requests for help, deployed five helicopters and asked for additional aircraft from New Orleans.