Pope Francis is calling the Las Vegas shooting a “senseless tragedy” and is assuring victims of his prayers.

The Vatican secretary of state sent a telegram of condolences Monday to the bishop of Las Vegas, saying the pope was “deeply saddened” to learn of the shooting.

The telegram said Francis praised the efforts of police and emergency crews.

In the deadliest mass shooting in modern U.S. history, a gunman opened fire on an outdoor concert, killing at least 50 people and injuring more than 400 others.