Snapshots of the 58 Utah homicides that occurred during 2013.

SALT LAKE CITY — Why did it happen?

In 2013, maybe more so than any year in recent memory, tragic homicides and violent deaths left loved ones, the public and even police investigators asking questions about motives that may never be answered.

• Why Draper Police Sgt. Derek Johnson was shot and killed without warning remains unknown. Johnson was just minutes away from ending his shift and just down the street from the police department when he was fired upon as he stopped to assist two stranded motorists.

• Just six days later, best friends Andrew Nelson, 15, and Ashton Peck, 13, were found dead, each from a single gunshot wound, inside Andrew's house in Murray. While police do not believe anyone else was involved, investigators say it's possible they may never know exactly what happened or why.

• In a similar case in November, two boys about the same ages as those in the Murray double shooting were found dead in the basement of a home in South Jordan. An autopsy determined that Taylor Wheeler, 12, was shot by his friend Dayton Gessell, 15, who then died of a self-inflicted gunshot wound. Police say they don't know if Dayton shot Taylor intentionally or if it was an accident.

• Brothers Alex Vidinhar, 10, and Benjie Vidinhar, 4, were found stabbed to death in their West Point home. Their 15-year-old brother was charged with two counts of murder in juvenile court. But why he allegedly killed his younger brothers, whom he was tending while his parents were out, remains a mystery.

The Deseret News recorded 58 homicides statewide in 2013, although investigators aren't sure whether two of those are homicides or suicides and may never know for sure. Six of those 58 people were shot and killed by police officers during 2013. While legally considered homicides, in all six of those cases the use of deadly force was determined to be legally justified because the officers' lives or the lives of others were in imminent danger.

And while homicides are more common in the state's most populated county, this year 33 of the 58 killings occurred outside of Salt Lake County.

Nearly half of the deaths occurred at the hands of family members, or people involved in personal relationships.

Twelve domestic-related murder-suicides occurred in 2013 involving husbands and wives, boyfriends and girlfriends, and in one case a girl and her stepfather. One incident involved a psychologist and his adult son in a national park, but investigators closed the case unable to determine definitively whether it was a murder-suicide or double suicide.

In at least half of those 12 cases, family members and neighbors indicated they couldn't understand why the killings occurred and never anticipated them.

In other homicides last year, even when detectives knew what happened, it didn't make it any less difficult to understand. For example:

• Ricardo Portillo, 46, was officiating a youth soccer game when he was punched by 17-year-old Jose Domingo Teran in the head. Portillo suffered a traumatic brain injury and remained in a coma for a week before dying. The motive for the attack: Teran said he was "frustrated" after receiving a yellow card.

• That same month, 5-month-old Ryker Petersen was shot in the head by his own father with a .22-caliber rifle. Joshua Petersen, 22, then tried to take his own life before he was stopped by family members. Petersen reportedly suffered from depression. The young dad was sentenced to life without the possibility of parole so he'll never be released from prison.

• In June, 2-year-old Chanse Drew died from blunt force trauma. Police say Bryson Drew, 21, killed his son before shooting and killing himself. But Drew's family said he adored his child and theorize that perhaps horseplay or another accident caused the boy's death, which led the father to write a suicide note before his own death.

Just weeks before, the father had written on Facebook: "I love my son Chanse more than anything in this world."

Drugs and gang violence continued to make its mark on Utah during 2013.

• Three people were found killed and a fourth injured in a single shooting spree in Midvale. Police say the home was a “known drug house." Unified police said they couldn't remember the last time they investigated a triple homicide.

• Sione Fakatoufifita, 19, was shot and killed outside a Maverik convenience store in Salt Lake City. Police say he was murdered simply for being a member of a rival gang.

• Anthony Hernandez, 18, was walking with a group in West Valley City when two vehicles pulled up to them and shots were fired, killing him. In addition to the alleged shooter, five others are also charged with murder for allegedly planning and orchestrating the killing of a rival gang member.

• Within a month, two homeowners in separate cases in South Salt Lake and West Valley City killed two men during home invasion robberies for drugs and money. One intruder was shot, the other was choked. Prosecutors did not file charges against the homeowners for the killings because their homes had been invaded and they were protecting themselves. Both homeowners, however, face drug-related charges.

Email: preavy@deseretnews.com, Twitter: DNewsCrimeTeam