The Queen has sent her "heartfelt sympathy" to US President Barack Obama and the American people after a horrific shooting spree at a cinema left 12 dead.
Another 59 adults and children were injured in the shooting in Aurora, Colorado, during midnight screenings of the new Batman movie.
The Queen's message said: "I was saddened to learn of the tragic loss of life earlier today in Denver, Colorado. Prince Philip joins me in extending our heartfelt sympathy to you and the people of America at this time.
"My thoughts and prayers are with the families of those killed and I wish the many who were injured a swift and full recovery."
She signed the message "Elizabeth R".
Mr Obama has described the shootings as "horrific and tragic" and said he is "shocked and saddened".
US police arrested 24-year-old James Holmes, whose apartment four miles away was booby trapped.
Aurora Police Chief Dan Oates said investigators are confident the gunman acted alone. Mr Oates added Holmes wore body armour, used an assault rifle, a shotgun and a Glock handgun. His car was parked at the back of the cinema.
Mr Oates said there were four showings of the film at the time and all were sold out. Some movie-goers said they thought Friday's attack was part of The Dark Knight Rises. Then they saw a silhouette of a person in the smoke at the front of the theatre, pointing a gun at the crowd.
It was the worst mass shooting in the US since an Army psychiatrist killed 13 soldiers and civilians at Fort Hood, Texas, in 2009, and brought memories of the massacre at nearby Columbine High School in 1999, where two students opened fire and killed 12 classmates and a teacher.