President Joe Biden on Sunday sought to comfort families in the Texas town of Uvalde following the nation’s deadliest school shooting in a decade as federal officials announced they would review law enforcement’s slow response.

Fury has mounted over the decision by law enforcement agencies in Uvalde to allow the shooter to remain in a classroom for nearly an hour while officers waited in the hallway and children inside the room made panicked 911 calls for help.

The President and first lady Jill Biden wiped away tears as they visited memorials at the Robb Elementary School where the gunman killed 19 students and two teachers, laying white roses at the school’s sign.

At the Sacred Heart Catholic Church in Uvalde, all the pews were filled as the Bidens attended mass. The Bidens will meet victims’ families, survivors and first responders.

The US Department of Justice on Sunday said it would review local law enforcement response at the request of Uvalde mayor Don McLaughlin.

Julian Moreno, a former pastor at Primera Iglesia Bautista and great-grandfather of one of the girls killed, said police made a huge error but that he felt “sorry for them because they have to live with that mistake of just standing by”.