Several hundred people gathered for a worship ceremony at a high school stadium in Texas on Wednesday evening to remember the at least 120 people who died in the catastrophic flash floods over the

Residents are clinging to hope as the search continues for Mark and Sara Walker and their 14-year-old son Johnny.

At least 120 people have died and some 173 people remain unaccounted for statewide, nearly a week after flash floods ravaged the Texas Hill Country.

Watch the terrifying moment a New Mexico home was swept away in raging floodwaters on July 8. Several people died in the storm.

"Let's put an end to the conspiracy theories and stop blaming others," Texas Agriculture Commissioner Sid Miller said in a statement.

Here's what to know about the deadly flooding, the colossal weather system that drove it and ongoing efforts to identify victims.

A flash flood is a rapid rise of water along a stream or in a low-lying urban area, the National Weather Service said. Flash flooding can result from slow-moving thunderstorms, from numerous thunderstorms that develop repeatedly over the same area, or from heavy rains associated with tropical cyclones.

Mourners gathered Wednesday night at Tivy High School's stadium, where they had celebrated victories and suffered losses on the field, said Ricky Pruitt, of the Kerrville Church of Christ. “Tonight is very different than all of those nights,” he said. Among those who died was the school's soccer coach.

A flash flood warning is in effect for parts of Massachusetts on Thursday morning, as forecasters call it a “dangerous and life-threatening situation.” The alert was broadcast around 8:15 a.m. on Thursday, and is in effect until 11:15 a.m.