By Ray Sanchez and Emma Tucker, CNN

Once again, a mass shooting has rocked Colorado -- this time, in Colorado Springs.

A 22-year-old gunman entered an LGBTQ nightclub in the city shortly before midnight Saturday and immediately opened fire, killing at least five people and injuring 25 others before patrons confronted and stopped him, police said.

At least two people inside Club Q confronted the gunman and prevented further violence, said Colorado Springs Police Chief Adrian Vasquez. The suspect used a long rifle in the shooting, and two firearms were found at the scene, Vasquez said.

The suspect is being treated at a hospital, police said. Officers did not shoot at him.

Colorado Gov. Jared Polis, a Democrat and the nation's first openly gay governor, issued a statement Sunday calling the attack "horrific, sickening and devastating."

There have been more than 600 mass shootings in the United States so far this year, according to the Gun Violence Archive. Since the 1999 massacre at Columbine High School, where two young men killed 13 people, Colorado has suffered several mass shootings:

Columbine shooting

The April 20, 1999, shooting changed the way police responded to all the active shootings that followed, with increased focused on targeting the shooter as soon as possible.

Nearly 50 minutes passed after the gunfire started before SWAT teams entered the school in Littleton. By then, 12 students and one teacher had been killed by the 17- and 18-year-old gunmen.

The shooters made home videos before the attack, with references to what they were going to do and apologizing to their parents for their actions. They then killed themselves.

The shooting at Columbine ranked as one of the worst mass shootings in US history at the time as well as one of the deadliest episodes of school violence.

Aurora shooting

A gunman opened fire on July 20, 2012, at a movie theater in Aurora, killing 12 people and injuring 70 others.

The shooting occurred 18 minutes into the midnight showing of "The Dark Knight Rises" at the Century Aurora 16 multiplex theater.

Authorities said the shooter was "dressed head-to-toe in protective gear" -- a ballistic helmet, protective gear for his legs, throat and groin, black gloves and a gas mask. He propped open a door before throwing tear gas canisters into the theater. After the canisters exploded, witnesses said he started shooting, first at the ceiling and then at the crowd.

He used an AR-15 rifle, a 12-gauge shotgun and at least one of two .40-caliber handguns police recovered at the scene.

On July 16, 2015, the gunman was found guilty on all 165 counts against him in connection with the massacre: 24 first-degree murder charges, 140 attempted murder charges and one count of possession or control of an explosive or incendiary device. He was sentenced to life in prison without parole.

Sheriff's deputy fatally shot, 4 law enforcement officers wounded

On New Year's Eve 2017, five law enforcement officers were shot and one of them, 29-year-old Deputy Zackari Parrish, was killed after a barricaded suspect opened fire at an apartment complex in Highlands Ranch, about 20 miles south of Denver.

Two civilians also were shot, and the suspect was shot and killed later by police, according to Douglas County Sheriff Tony Spurlock.

"This is a tragic day that we will be feeling for a long time," Spurlock said. "Zack was a good kid, smiley kid. He was eager to work, eager to serve."

The 37-year-old suspect had barricaded himself in a bedroom before he suddenly opened fire with a rifle, hitting four deputies in the apartment, authorities said.

"There were well over 100 rounds fired ... from the suspect," Spurlock said.

STEM School Highlands Ranch shooting

On May 7, 2019, two gunmen opened fire at a Denver-area charter school, killing 18-year-old student Kendrick Ray Castillo and injuring eight others.

The shooting occurred at STEM School Highlands Ranch, just miles from Columbine High School.

One of the suspects was found guilty of first-degree murder in June 2021, among a list of other charges, while the other suspect pleaded guilty in early 2020 to 17 counts, including murder charges.

"If you had suggested to anyone behind me, or in this room, that in 20 years in 20 miles we would have dealt with Columbine, Aurora theater, Arapahoe High School, the shooting of Zack Parrish and four other deputies, we'd have thought you mad, yet here we are again," District Attorney George Brauchler said after the shooting.

He added, "This does not define us, it won't today, and it won't tomorrow. These are abhorrent acts. Problem is when you get three, four or five of them within a 20-mile radius you begin to think they are less abhorrent. But I'm here to tell you, this is not who we are."

Boulder grocery store shooting

A gunman had just shot an elderly man outside the King Soopers in Boulder on March 22, 2021 before entering the store and opening fire.

Ten people were killed in the shooting. The victims included employees, customers and Boulder police officer Eric Talley, a father of seven who was gunned down seconds after he rushed into the store, police said.

About 115 people were inside the store and at least 25 were in the parking lot when the attack happened.

The 22-year-old gunman received over 50 charges, including 10 counts of murder and one count of attempted murder. He was deemed "incompetent to stand trial currently" by a doctor, according to Boulder County District Attorney Michael Dougherty, following a second court-ordered competency evaluation.

6 killed at Colorado Springs birthday party

On May 9, 2021, six people were killed during a birthday party at a Colorado Springs mobile home, police said.

Officers responded to the Canterbury Mobile Home Park, where they found six dead adults, along with a seventh person who was injured and later died at a hospital.

The suspected shooter, who was believed to be a boyfriend of one of the victims, also died, police said. The suspect drove to the home where a birthday party was being held and opened fire before killing himself, according to police.

"As the chief of police, as a husband, as a father, as a grandfather, as a member of this community, my heart breaks for the families who have lost someone they love and for the children who have lost their parents," Colorado Springs Police Chief Vince Niski said after the tragedy.

Six teens injured in Aurora shooting

On November 15, 2021, six teenagers were wounded in a shooting involving multiple suspects at a small park close to a high school in Aurora, police said.

Six students who attend nearby Aurora Central High School went to the hospital. One student drove themselves, said Police Chief Vanessa Wilson.

The victims were a 14-year-old boy, a 15-year-old girl, a 16-year-old boy, a 16-year-old girl, a 17-year-old boy and an 18-year-old male, police said.

"My understanding is it was a drive-by shooting, as well as there may have been people on foot," Wilson said.

"I think enough is enough. And I think we need to come together as a community," Wilson said. "This is a public health crisis."

Gunman opens fire across Denver area

On December 27, 2021, a gunman killed five people and wounded several others, including a police officer, in a Denver metro area shooting spree that included a car chase and gunfights with law enforcement, authorities said.

The gunman allegedly opened fire at multiple locations in and around Denver, including in the suburb of Lakewood, about 8 miles west of downtown Denver, Denver Police Chief Paul Pazen said.

Denver police identified a vehicle linked to the incident and gave chase, leading to a gunfight between the suspect and officers, the chief said.

The 47-year-old gunman was killed after a gunfight with a police officer.

The gunman opened fire in several different locations, including the busy South Broadway neighborhood, a shopping center and near the emergency department at Denver Health Medical Center.

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