Children's lives could have been saved if police had acted sooner when a gunman opened fire at an elementary school in Texas - according to a US justice department investigation.
The damning report details "critical failures" in the response, as roughly 400 officers waited for more than an hour while a gunman continued his massacre inside two classrooms.
19 students and two teachers were killed.
Kate fisher reports from Washington
IN: the nearly
OUT: for help
DUR: 52"