"Death inundated them from a thousand sources" what does it mean?​

It overwhelmed them.

Explanation:

The death(of someone) overwhelmed them(someone) from a thousand sources (for many reasons or many places or many things)

Hope it helped.

Explanation:

At least 25 people have died in China's flood-stricken central province of Henan, a dozen of them in a subway line in its capital Zhengzhou, and more rains are forecast for the region.

About 100,000 people have been evacuated in Zhengzhou, an industrial and transport hub, where rail and road links were disrupted. Dams and reservoirs have swelled to warning levels and thousands of troops are taking part in the rescue effort in the province.

Twelve people died and more than 500 were pulled to safety after a subway tunnel flooded, state media reported, while social media images showed train commuters immersed in chest-deep waters in the dark and one station reduced to a large brown pool. read more

"The water reached my chest," a survivor wrote on social media. "I was really scared, but the most terrifying thing was not the water, but the diminishing air supply in the carriage."

The rain halted bus services in the city of 12 million people about 650 km (400 miles) southwest of Beijing, said a resident surnamed Guo, who had to spend the night at his office.

"That's why many people took the subway, and the tragedy happened," Guo told Reuters.