Johnny Tapia, a five-time boxing champion whose controversial personal life included several run-ins with the law as well as addiction to cocaine and alcohol, was found dead on Sunday in his home in Albuquerque, N.M. He was 45.

At about 7:45 p.m. MDT (9:45 p.m. EDT) on Sunday, authorities were called to Tapia's house to investigate. He was found dead at the scene, reported the Associated Press. Police said his death does not appear to be suspicious, but they are still investigating. They did not say how he died.

Dennis Latta was a longtime friend of Tapia. The former sportswriter spoke with his family and said they are just distraught, reported KOB.

He's come so close so often to death, so it's hard to believe that it's finally happened, Latta said.

Latta described some of his friend's near-death experiences, noting that Tapia always fought back. I remember in [Las] Vegas one time he was in a coma for days, and they didn't think he was going to make it -- he was in critical condition, Latta said. To realize that now he's gone, it's really a surprise, I thought he was just invulnerable, it was water off a duck's back every time he came close to death.

Tapia had a difficult childhood. When he was 8, he witnessed his mother's kidnapping and murder as she was she chained to the back of a pickup truck as it drove away.

However, a young Tapia turned to boxing as a way to channel his emotions. He began his professional career in 1988. He won eight fights in his first year, five by knockout. In the ring, he quickly rose through the ranks and became a nationally recognized fighter, reported NESN.

In 1990, Tapia captured the U.S. junior bantamweight title. Throughout most of his life, however, he battled depression and addiction. And, later that same year, he was suspended from boxing after he tested positive for cocaine.

In 1994, Tapia claimed he kicked his habit and returned to boxing, but Albuquerque police placed him under arrest after they found cocaine in a bag he was carrying, reported KOB.

However, Tapia was regarded as an underdog figure -- and the more trouble he had in his personal life, the more his fans rallied behind him, reported the AP.

The charges were dropped, and Tapia began a feud with fellow Albuquerque-bred boxer Danny Romero, which culminated in a 1997 bout that Tapia won.

In 1999, depression began to take its toll on Tapia as he attempted suicide by overdosing on drugs. He came close to death again in 2007 because of an overdose -- unintentional this time -- reported KOB.

But Tapia kept fighting back and said he loved the challenges of life.

I love the challenge, Tapia said during a 2000 interview with NewMexicoBoxing.com. Today everybody knows that I change trainers like switching my shorts. But the minute I start learning about boxing I'll quit. I can just walk out . . . Well, I don't know, it's gonna be hard for me because I've been doing it now for 26 years. But y'know, I love the challenge. And it's kept me living in life. For bigger and better things.

However, Tapia was arrested on drug-related charges many more times. His most recent arrest came in 2009 when he was charged with violating parole.

Tapia's final fight was held last June. He defeated Mauricio Pastrana in an eight-round bout, as he ended his career with a 59-5-2 record.