As he drove up, Johnson, 32, was "ambushed" by the man in a silver Volvo, who also shot the 34-year-old woman with him, Roberts said. As Johnson drove from the area, the man continued shooting, and Johnson crashed into a tree three blocks north, at about 12900 S. Fort St., the chief added.
"[He] was never able to return fire," Roberts said.
After shooting at Johnson, the man turned the gun on himself, Roberts added.
Dispatchers received an unintelligible distress call from Johnson at about 6 a.m. More calls, this time from citizens, quickly followed about shots fired. Emergency responders rushed to the area of Fort Street, a residential neighborhood, where witnesses say they found Johnson wounded in his police vehicle; they pulled him out and tried to save him. He was flown to Intermountain Medical Center but died of his injuries.
Officers also found the male suspect and female victim, who were taken to local hospitals in critical condition. Investigators later determined that the man and woman had been in an accident at 900 East and 13800 South, striking fixed objects, and kept going until they came to a stop at 13200 S. Fort St., where Johnson came across them.
Kris Szelag, who lives in the 12900 block of Fort Street, said she was awakened by a gunshot and then heard what sounded like a car crash.
She looked outside and saw officers pull another officer out of a police car and perform CPR until a Life Flight helicopter landed and carried the officer away. She said her adrenaline was high.
"I wanted to see if there was any way I could help," said Szelag, who is an RN.
Officers cordoned off a large swath of Draper neighborhoods, from 300 East to 1300 East and from Pioneer Road to 13800 South. Church services were canceled, and residents within the containment area were asked to stay in their homes through a reverse 911 call and a phone tree as armed officers patrolled the streets with police dogs.
"We want to reassure the residents that we are doing everything we can to keep the residents of Draper safe," Roberts said.
"It brought back shades of the Boston [manhunt]," said Draper Councilman Bill Rappleye, who lives in the search area. "It's a sad day any time one of our officers is injured in the line of duty, or worse. It's a heartbreaker."
The perimeter was eventually narrowed to Fort Street between Walden Lane and 13300 South. The chief said police are asking everyone there to stay in their homes and contact an officer on-scene if they need to leave. An officer will then escort them out of the area.
The Unified Police Department is investigating the shooting. Police will continue to update residents as information becomes available, Roberts said.
Johnson is the 136th law enforcement officer to be killed in Utah in the line of duty.
Phil Goold has known Johnson most of the police sergeant's life through their local LDS Church ward.
"He married his high school sweetheart who lived around the corner from him," said Goold, adding that Johnson married his wife, Shante, shortly after high school graduation.
About the same time, Johnson entered the police academy.
"Derek always wanted to be a police officer," said Steve Glad, who used to be a bishop in Johnson's LDS ward. "It was his dream from when he was a little boy."
Johnson was hired in April 2004 as a Draper reserve officer and made a full-time officer eight months later. He was then promoted to sergeant in December 2012, working in patrol, community policing and investigations. He also received a community policing award that year.
"I've known Derek for many years," said Draper Mayor Darrell Smith. "He is one of the best and most qualified sergeants on our force. … Never have I spoken with Derek without recognizing his positive attitude and love for his work and serving the community of Draper."
Johnson did a good job protecting his hometown, Goold added.
"Derek was just a good kid, a local kid," Goold said. "I remember going on outings with him. We had an annual pilgrimage out to Moab as men, a boys' weekend thing. ... [The Johnsons] really were this great Draper family."
He leaves behind his wife and a young son.
The 1033 Foundation, which provides immediate financial assistance to the families of fallen officers, privately presented a $25,000 check to the Johnsons on Sunday afternoon.
"Every time a police officer dies in the line of duty, we'll be there that day," said Ryan Walsh, a member of the board of advisers. The radio code 10-33 means an officer is in urgent need of help.
This is third time the Park City-based foundation has given such assistance. The first time was after the January 2012 death of Jared Francom, an Ogden police officer killed while serving a search warrant.
The second time was in June 2012, after Utah Highway Patrol Trooper Aaron Beesley died after falling from a cliff during a search and rescue mission near Mount Olympus.
"We've gone 13 months without a line-of-duty death," Walsh said. "We would have liked to go longer."
Sunday afternoon, Nevah Stevenson left a bouquet of yellow roses on the steps of Draper City Hall. Stevenson, school advancement director at St. John's the Baptist Elementary and Middle School and a Draper resident, saw a Facebook post about tying yellow ribbons around the city in Johnson's honor hence her color choice for the flowers.
"I have a heavy heart," she said. "I am praying for his family."
A note with the flowers reads: "Holding you in our hearts, Johnson family. May God bless officer Derek Johnson."
A candlelight vigil was held at 8 p.m. at Draper City Hall to honor and remember Johnson.