2021 ended with a shooting rampage that shocked the Denver metro area.

On Dec. 27, a gunman killed five people and injured two others in Denver and Lakewood. He shot Lakewood police officer Ashley Ferris, who the department says returned fire, killing the gunman.

The rampage capped a year of 96 homicides in Denver, its largest total in at least three decades. According to the Denver Police Department, those statistics exclude fatal shootings by police.

Denver’s homicide rate for 2021 was 1.3 per 10,000 people. That’s slightly lower than the homicide rate in 1993, at 1.6 per 10,000 people, adjusted for population growth. That year was termed the “summer of violence” by some media and public officials, even though homicides were lower in 1993 than in the previous two years.

The lowest number of homicides recorded in Denver since 1990 was 31 in 2014. The rate that year dropped to 0.49 per 10,000 people.

Through the spikes and ebbs in homicide numbers, opinions on what contributes to the violence vary as much as the circumstances of each homicide. Substance abuse is a commonly cited contributor, linked to a person’s desperation for money to fuel their dependency or disconnection from reality. Some point a finger at supervision and sentencing policies they say are too lax, allowing dangerous people back on the streets too easily. Others say gangs are behind brash acts of violence.

COVID-19 has also alarmed those watching crime statistics, who say myriad factors linked to the pandemic could be contributing to crime, such as economic instability, reductions in arrests or difficulty accessing support services.

“I think that it’s hard to pin it down,” said Denver District Attorney Beth McCann. “I personally think that the more resources we can put into the upfront causes of crime, the better off we will be in the long run. And those are things like employment opportunities, education, support for families, substance abuse and mental health treatment, all of those things.”

The family of the gunman in Monday’s rampage implied in a statement that he may have had a mental illness that wasn’t properly addressed. The killings show a “deep need for a system geared toward helping mentally-ill individuals,” they said, though the statement didn’t elaborate. His family had been estranged from him for years, they said.

“We lost our son and brother years ago. We mourn the loss of life and injuries caused by this horrendous crime.”

While mental illness can be a driver of violent acts, McCann cautioned against leaning on it too heavily as a contributor, since most people who live with mental illness don’t commit violence.

Gov. Jared Polis said the state will “redouble” crime-fighting efforts following the rampage, saying it shows a need to increase support for law enforcement, more policing and making sure people who commit crimes are detained and convicted.

“Just a horrific, horrific tragedy. … He obviously didn’t get the help that he needed,” Polis said in a news conference last week when asked about the rampage.

Police and the district attorney share concerns about the role played by so many guns in circulation, especially those obtained illegally. By late July, officers had taken nearly 1,200 illegal guns off the streets when the police department announced a partnership with the Bureau of Alcohol, Tobacco, Firearms and Explosives to investigate cases of people unlawfully possessing guns.

In 2020, 21-year-old Isabella Thallas was killed in Denver’s Ballpark neighborhood, and it later came out the suspect used a gun that belonged to a Denver police officer. Following her death, state lawmakers passed a bill in 2021 that requires gun owners to report a loss or theft to law enforcement within five days of the discovery.

Denver police have also expressed concerns in recent months about homicides committed by people on mandated supervision, be it probation, parole or pretrial supervision. Police Chief Paul Pazen previously told a City Council working group that a few dozen people accused of committing homicides were on court-ordered supervision.

The victims “could be alive today if other parts of (the) criminal justice system were working as designed,” he said.

Denver police declined an interview for this article, saying they preferred to wait until after the end of the year to talk about 2021’s homicides in totality.

McCann said in a later presentation to the working group that prosecutors have to strike a difficult balance between protecting public safety and avoiding holding people in jail who haven’t been convicted of crimes.

“We’re trying to be as reasonable and responsible as we can be, but also understanding that holding someone in jail before they’ve been convicted of a crime is very disruptive to that person’s life, their family and their jobs.”

McCann said ideological divides in how to approach reducing crime can be difficult to overcome, but she said people should be able to find common ground when it comes to community safety — something everyone wants.

Gun regulations, she said, are one example of an issue that she doesn’t see everyone agreeing on. But heartache and damage done by proliferation of fentanyl is another problem people should be able to come together on for solutions, McCann said.

“I think we can come together on some areas and talk about solutions, because I think we all want crime to stop. So we just have a different approach or a different emphasis, perhaps.”