The current 911 system handles around 230 million calls per year with most of the calls being from mobile phones. One situation influenced this move to allow texting to 911 was the Virginia Tech shooting.
“The technological limitations of 9-1-1 can have tragic, real-world consequences,” the release said. “During the 2007 Virginia Tech campus shooting, students and witnesses desperately tried to send texts to 9-1-1 that local dispatchers never received. If these messages had gone through, first responders may have arrived on the scene faster with firsthand intelligence about the life-threatening situation that was unfolding.”"
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