Vigil participants read a list of names of those killed in recent gun violence around the nation and talked about the pain of losing loved ones as they called for strict federal gun control laws.
"Why wait any longer?" asked Carlee Soto, whose sister was killed at the Sandy Hook Elementary School rampage in Newtown, Conn. "The time for change is now."
Mayors Against Illegal Guns, which promotes tough gun laws and was founded by New York City Mayor Michael Bloomberg, helped sponsor the vigil.
The scene was somber, even as about 100 gun rights activists held a protest nearby to oppose new firearms restrictions as infringements on Second Amendment rights. Many wore orange National Rifle Association hats and T-shirts reading, "I will not comply."
"To the families and victims of the tragedy, we offer our condolences and prayers," said Dudley Brown, executive director of Rocky Mountain Gun Owners. "To Mayor Bloomberg and the group that would politicize this, we offer our opposition."
Brown helped organize the rally and carried a .45-caliber pistol to the park.
The shooting victims, meanwhile, called for more universal background checks and tighter restrictions on gun sales. Colorado has been the only state outside the East Coast to ratchet back gun rights in reaction to last year's mass shootings. A recent push for new federal restrictions failed in Congress.
"I think that Coloradans get it, that something must change," said Tom Sullivan, whose son Alex was killed in the theater.
Just before their rally started, one gun rights activist, Rob Blancken, tried to stand behind a lectern with a sign that read, "Tell billionaire Mayor Bloomberg to stay the hell out of Colorado." He was told to move by a state parks ranger.
Gun rights organizers said they sympathized with the victims but didn't see new gun control laws as a solution.
"We want the families of the victims to know that we are sorry for their loss," said Alicia Perez, a Colorado organizer with Gun Rights Across America.
For his part, Stephen Barton, who was wounded in Aurora, said, "You shouldn't wait until it affects you to start caring about it."
"I never thought I would ever be affected by gun violence personally," Barton added.
Mayors Against Illegal Guns said participants were reading the names of about 2,500 people who have been killed by gunfire since Dec. 14, when a gunman killed 20 first-graders and six adults at Sandy Hook.
The Aurora vigil came almost a year to the day after 12 people were killed and 70 others were wounded, some paralyzed, in a July 20 attack at a midnight showing of "The Dark Knight Rises."
The victims' names were being read until 12:38 a.m. Saturday, the moment that the shootings began in the theater last year.
The theater planned no midnight showings on July 20 this year.
At least eight uniformed police officers were at the theater complex Friday, including one inside the auditorium where the shootings took place.
Dallas Hill of Aurora, who was among about 30 people who watched "Red 2" in that theater Friday night, said he had no qualms about being there.
"We've been in there several times before," he said. "The first couple times (after the shooting) it was a little eerie," he said.
Denver Archbishop Samuel J. Aquila, accompanied by more than 20 white-robed priests, led a memorial Mass for the theater victims Friday night at St. Michael the Archangel Catholic Church in Aurora.
"Sin, violence and evil does not have the final word," he said in his homily.
Names of those killed alternated on video screens outside the sanctuary.
Remembrance events planned for Saturday included an early morning memorial service and a host of volunteer civic works, music, arts and even meditation. Aurora officials say they wanted to promote healing.