Pyle couldn't comment on Nielsen's medical history, but said that the origin of the problem goes back longer than the 15 years he's known him.
He was even born with medical problems, according to a 2011 video interview with The Tribune.
"I guess I was always crying," Nielsen said, "[So] my grandma named me Buzz, and it worked and it stuck and then when I got to school, nobody could say Thayle, so I was always embarrassed growing up, so I stuck with the name of Buzz."
Nielsen made chief in 2002, having joined West Valley City as a patrol officer when the city incorporated in July of 1980.
Since then West Valley City has grown into the second-largest municipality in the state with 132,000 residents.
The property crime rate declined by 23 percent from 2002 to 2010, according to FBI data. The violent crime rate increased 19 percent in that span.
Nielsen and his department have been in the spotlight since December 2009, when Susan Powell disappeared from her West Valley City home.
Powell has never been located. The only person of interest in the case, her husband Josh Powell, killed the couple's two sons then himself Feb. 5, 2012, in Graham, Wash.
Attorneys representing Susan Powell's family have accused West Valley City police of making mistakes in the investigation. But on Friday, her father Chuck Cox wished Nielsen well.
"I don't blame him for anything," Cox said. "I think he did the best that he could and think [West Valley City police are] continuing to do the best they can."
In the 2011 interview, Nielsen pointed to Susan Powell's case as one of the most interesting moments in his career, as well as the murder of Margo Bond. The John F. Kennedy Junior High School janitor disappeared in 1992 and her husband was considered a suspect. But a father and son found her corpse her arm bone was protruding from a shallow grave in Tooele County and Roberto Arguelles, a Utah State Prison inmate, confessed to killing her when he was out on parole that year.
Nielsen also said that he considers law enforcement the best profession, one in which he could see the difference they made "then and there."
Councilman Don Christensen, whose son is a WVCPD officer, spoke highly of Nielsen's effort to work with other agencies along the Wasatch Front to buy resources, like ammunition and vehicles, at a bulk rate.
On top of that he "was a cop's cop," Mayor Mike Winder said, who was "extremely dedicated to what he was doing."
Schwemmer takes over during the ongoing investigation into the death of 21-year-old Danielle Willard, who was unarmed when she was shot and killed by two West Valley City detectives on Nov. 2 of last year. Willard's family and supporters have held multiple protests and vigils over the shooting.
Nate Carlisle contributed to this report.