Mr. Sizemore died in his sleep after suffering a brain aneurysm Feb. 18, which occurred as a result of a stroke, Charles Lago, his manager, said. Sizemore remained unconscious and in critical condition until his death.
Mr. Sizemore acted professionally for more than three decades and developed a reputation, a reporter for his hometown Detroit News once observed, “as a character who lives on the edge, both on film and in real life.”
He landed one of his first notable roles in “Natural Born Killers” (1994), playing a sadistic detective in a cast led by Woody Harrelson and Juliette Lewis under the direction of Oliver Stone.
The following year, he appeared with Al Pacino and Robert De Niro in “Heat,” a crime drama directed by Michael Mann. Mr. Sizemore later starred on the police procedural “Robbery Homicide Division,” which aired on CBS from 2002 to 2003 with Mann serving as an executive producer.
Mr. Sizemore, TV critic Tom Shales wrote in The Washington Post, provided “the key performance” as Detective Sam Cole, “head of one of those elite teams inside the police force that get to dress well and barge in without search warrants.” He “veritably storms the screen in one of those can’t-look-away performances,” Shales wrote, “that make a character instantly indelible.”
By the late 1990s, the range of roles available to Mr. Sizemore had begun to broaden. He played the second-in-command to Tom Hanks’s determined captain in “Saving Private Ryan” (1998), director Steven Spielberg’s World War II film.
Mr. Sizemore returned to the on-screen battlefield in “Black Hawk Down” (2001), about the 1993 military operation in Mogadishu, Somalia, in which 18 U.S. soldiers died.
“It’s starting to get wider for me,” he told the New York Times in 1999. “I’m being offered more sensitive tough cats, guys who’ve been through a violent episode or two and had a propensity to violence but now come down on the side of good.”
But around that time, Mr. Sizemore faced personal and legal problems that he attributed to substance abuse. By his account, he abused alcohol before moving to cocaine, then heroin and crystal meth.
In 2003, Mr. Sizemore pleaded no contest to a misdemeanor charge after a former girlfriend, Brooke Ford, alleged that he had hit her and dragged her across the floor.
Also in 2003, he went on trial on misdemeanor charges stemming from his alleged abuse of another girlfriend, Heidi Fleiss, the former Hollywood madam who met Mr. Sizemore after her release from prison for conspiracy, tax evasion and other offenses.
Mr. Sizemore, who had previously been married to actress Maeve Quinlan, attributed his attraction to Fleiss to a “classic midlife crisis, coupled with a divorce I didn’t want, and loneliness.”
Fleiss cried on the witness stand as she recounted that Mr. Sizemore assaulted her, broke her belongings and threatened her. He was convicted on multiple misdemeanor charges and sentenced to six months in jail and three years of probation, with his sentence stayed until after he had undergone drug rehabilitation.
“I have permitted my personal demons to take over my life,” Mr. Sizemore wrote in a letter to the judge. “I do not want to make excuses, but I am convinced that if I had not been under the influence of drugs, I would have controlled my behavior.”
In the years that followed, Mr. Sizemore was repeatedly arrested for drug and battery offenses. He continued acting through his travails, appearing in dozens of movies and TV series including “Crash,” “Hawaii Five-0,” “Shooter” and “Twin Peaks.”
Thomas Edward Sizemore Jr. was born in Detroit on Nov. 29, 1961, according to his manager. His father taught philosophy at Wayne State University and later became a lawyer, and his mother worked for the city government.
Referring to several relatives who had been convicted of drug and prostitution offenses, Mr. Sizemore said that he came from “a very mixed bag.”
He was drawn to acting, he said, in part by director Martin Scorsese’s 1976 psychological drama “Taxi Driver” starring De Niro, which Mr. Sizemore saw when he was 14.
“Almost immediately, I knew I wanted to be an actor, but I had to keep it secret,” he told the Times. “I was from the east side of Detroit. It was not something you said you wanted to do. It would be akin to me saying I want to go to the moon on the next flight.”
Years later, De Niro again played an important role in Mr. Sizemore’s life when he persuaded him at one point to enter drug rehabilitation.
Mr. Sizemore studied theater at Wayne State, where he received a bachelor’s degree in 1983. He continued his theatrical studies at Temple University in Philadelphia, receiving a master’s degree in 1986 before moving to New York.
He began acting in plays and caught the attention of a casting director who invited him to audition for a bit part in Stone’s anti-Vietnam War film “Born on the Fourth of July” (1989).
Mr. Sizemore also landed parts in gritty movies including “Lock Up” (1989) with Sylvester Stallone and “Passenger 57” (1992) with Wesley Snipes.
His other film credits included “Guilty by Suspicion” (1991), a 1950s blacklist-era story starring De Niro; “Devil in a Blue Dress” (1995), a detective drama with Denzel Washington; and “Strange Days” (1995), a thriller with Ralph Fiennes, Angela Bassett and Lewis. In 1998, he played John Gotti in the TV movie “Witness to the Mob.”
At his peak, the Los Angeles Times reported, Mr. Sizemore earned $4 million per film. He lived in a home in Los Angeles’ Benedict Canyon that was owned earlier by actor Gary Cooper, but he was forced to sell the property as his financial and legal problems mounted. He said he lost a total of $18 million, ultimately filing for bankruptcy.
Mr. Sizemore’s troubles were chronicled in “Shooting Sizemore,” a TV series that aired on VH1 in 2007, and the reality TV shows “Celebrity Rehab” and “Sober House.” He was the author of the 2013 book “By Some Miracle I Made It Out of There: A Memoir,” written with Anna David.
Mr. Sizemore had twin sons, Jagger and Jayden, from a relationship with Jinele McIntire.
In 2007, a reporter for the Los Angeles Times asked Mr. Sizemore if he had anticipated the turns that his life would take.
“Absolutely not,” he replied. “Did I know I would declare bankruptcy, publicly humiliate myself and be excoriated in the press? Of course not. Had I known that, I might have gone home [to Detroit] and worked at General Motors. Actually, I don’t know if I would have done that either. I love acting.”
To anyone who thought that drugs are “cool, a viable choice on how to live your life,” he added, “you’re wrong. I am a living, breathing example of what can happen.”