Officials said the officers were serving a search warrant on a home as part of a drug investigation on Wednesday night in the city of Ogden, north of Salt Lake City. When there was no answer at the door, they entered and were fired upon.
Witnesses said they heard what sounded like automatic gunfire.
When it was over, a 7-year veteran officer, Jared Francom, was dead and five other officers were wounded, some critically.
"It's a very, very sad day," an emotional Ogden Police Chief Wayne Tarwater said Thursday.
The wounded officers were taken to a hospital. The suspect, 37-year-old Matthew David Stewart, was at a local hospital under guard. His injuries were described as not life threatening.
Investigators said Stewart, an Army veteran, has a limited criminal history. According to his estranged father, he suffers from post-traumatic stress disorder and may have been self-medicating with marijuana.
Francom is survived by a wife and two children. In an interview with Salt Lake City's ABC 4, Erin Francom said her husband "loved his job more than anything" and that he was a great father to their daughters. She said the girls, ages 5 and 3, are having a tough time understanding the loss of their father.
The Associated Press contributed to this report.