Bomb squad experts will try again Saturday, July 21 to enter a gunman's booby-trapped apartment, hours after a late-night vigil for the 70 victims of a massacre in a packed cinema, including 12 dead, AFP said.

Hundreds of mourners held candles, many sobbing and hugging each other in an outpouring of grief for those who died when the gunman opened fire in a packed cinema showing Batman movie "The Dark Knight Rises."

The shooting drew expressions of concern from political leaders led by President Barack Obama, and revived the perennial debate about gun control in the United States.

Bomb squad experts had been trying for much of the day Friday to gain entrance to the apartment since shortly after the shooting in the town of Aurora, just outside Denver, Colorado.

But they gave up shortly before sundown, and said they would resume again Saturday, when they hope to make a breakthrough that could also reveal clues as the motives of gunman James Holmes.

Late Friday the town gathered for two vigils, including a midnight one, as it emerged that the alleged gunman bought more than 6,000 rounds of ammunition on the Internet, and four guns, in the two months before the shootings.

The masked, black-clad shooter, named as James Holmes, 24, burst into a movie theater barely 20 minutes into the midnight screening of "The Dark Knight Rises," throwing two tear-gas type devices before opening fire.