Bernhardt Tiede II is the son of Bernhardt Tiede (1912–1973), a native of Olgenow, Russia (previously Ukraine) of German descent who had immigrated with his family to the United States in 1926. Bernhardt Tiede (Sr.) had served as a professor of music and choral Director at Our Lady of the Lake College (now Our Lady of the Lake University) in San Antonio, Texas (1946–1948), at Southern Methodist University (SMU) in Dallas, Texas (1948–1957), at Kilgore College in Kilgore, Texas (1957–1968), and then at McMurry College (now McMurry University) in Abilene, Texas, where he served as Director of the McMurry Chanters, the position he held until his death in 1973. In addition to his work as a university professor, the elder Tiede also served as church music Director and as a vocal performer. Bernie Tiede's mother was Bernhardt Tiede Sr.'s first wife, Lela Mae Jester (1933–1960). They were married in 1957, and Bernie was born in the next year. But Bernie's mother died in an automobile accident when he was two years old. In 1963 his father married Clara Kathryn Wiley (b. 1938), who became Bernie's stepmother. His father died in Abilene, Texas when Bernie was fifteen. Bernie Tiede graduated from Cooper High School (Abilene, Texas) in 1976.

Tiede met Nugent in March 1990 at her husband's funeral, with which Tiede helped while assistant Director at Hawthorn Funeral Home. The two eventually became inseparable. In 1991, Nugent altered her will and disinherited her son, leaving her entire $10 million estate to Tiede. By 1993, Bernie left his job to work for her full time as her Business manager and travel companion.

This differs greatly from other witnesses' testimonies as Gregg County Commissioner Darryl Primo testified that in a conversation he had with Marjorie between 1991 and 1996 that she spoke well of Bernie's spending, stating, "I’ll spend every dime [of my money] before I leave it to my family." Additionally Merrell Rhodes, the victim's sister, spoke of her feelings toward Marjorie saying "I was always afraid of her...I never forgot that she was my sister... I always loved her as a sister, actually, even when she did ugly things, and she did." Merrel's son, Joe Rhodes, attested to the movie's accurate portrayal and mentioned several acts of his aunt's abuse toward him in the New York Times article "How My Aunt Marge Ended Up in the Deep Freeze".

In November 1996 Tiede killed Nugent by shooting her in the back four times with a .22 rifle. He then placed Nugent's body in a freezer used to store food at her Carthage home. According to the Amarillo Globe-News, Nugent's estranged son, Amarillo pathologist Rod Nugent, traveled from Amarillo to Panola County nine months after her death, where he declared Nugent a missing person. After entering Marjorie's residence, Rod and his daughter found his mother's body in the freezer, wrapped in a white sheet.

Tiede was taken in for questioning, and he admitted to Nugent's murder to police in August 1997. Tiede stated that after the murder, he cleaned the body and placed Nugent in a freezer. After this, Tiede admits, he had given gifts to several friends in Carthage using Nugent's money, which she had previously given him power of attorney to use.

Shortly after entering the Texas Department of Criminal Justice in 1999 Tiede was attacked by fellow inmates. During his imprisonment, Bernie was described by a prison official as "a model prisoner," teaching health classes and participating in the prison's choir. He had been, until May 2014, serving a life sentence. However, District Attorney Danny Buck Davidson and a visiting Judge Diane DeVasto of Tyler, Texas, allowed him to be released from his life sentence that month on $10,000 bail, after the appeals attorney for the case, Jodi Cole, discovered that Tiede had been sexually abused as a child for multiple years. Cole alleged that Tiede shot Nugent while in a brief dissociative episode brought on by his abusive relationship with her, a theory backed by forensic Psychiatrist Richard Pesikoff.

It's also been suggested that Tiede's handwritten confession (a major factor in the murder being considered first-degree) was heavily influenced by threats of leaking private video tapes of Tiede. When presented with the new evidence, Davidson agreed that had he known this information in the original trial he would have sought a lighter sentence. Nugent's family heard about the release through media reports. Her granddaughter expressed shock that the release was granted and claimed that Richard Linklater's 2011 film Bernie had influenced the legal system. The Nugent family created a website to honor Nugent's memory, posting photos of her and articles relating to her murder.

Between the time of his release in 2014 and his resentencing in April 2016 Tiede resided in Austin, Texas, in filmmaker Richard Linklater's garage apartment, which was a condition of his release.

As of 2016 Tiede resides in the Telford Unit of the TDCJ. A week after his resentencing, his lawyers filed an appeal to the court's decision. In June 2016, the 1997 theft charge against Tiede was dropped. In August 2017, a Texas appeals court upheld the 99-year prison sentence.