HIRAX began in Los Angeles in 1984, but because of the weak metal scene in the area, spent most of their time playing in San Francisco along with Slayer, Metallica, and Exodus, who were all part of the exciting new metal emerging from the Bay area. The original line-up was Katon W. De Pena (vocals), Bob Savage (guitar), Gary Monardo (bass), and Brian Keith (drums). They released a four-song demo in 1984. Their songs at the time were more similar to the British metal bands such as Saxon, Tygers of Pan Tang, Judas Priest, Iron Maiden and the New Wave of British Heavy Metal period. This demo was widely circulated and the band became known and respected worldwide through the metal tape trading underground. Later in '84, guitarist Scott Owen and drummer John Tabares replaced Savage and Keith. Influenced by such great acts as Motorhead, Anvil, and Venom, Vocalist De Pena wanted the band to go in a heavier and faster direction musically; and HIRAX's thrash metal style was born.

Because of their notoriety in the underground, HIRAX were signed to Metal Blade Records and recorded a track for the legendary compilation "Metal Massacre VI," which also featured Slayer, Voivod, Celtic Frost, Fates Warning, Metal Church, and Trouble. HIRAX contributed "Bombs of Death,” which was the first song recorded with the new line-up. The bands on the "Metal Massacre VI" compilation were all at the forefront of a new metal movement and the record sold well.

In 1985, HIRAX included “Destruction And Terror” on the compilation "Angelican Scrape Attic" 7” flexi disc, which was Earache Records’ first release. They were the only U.S. band featured on the limited edition compilation. HIRAX were gaining fans at a rapid pace. HIRAX released their first full-length recording in 1985 on Metal Blade titled "Raging Violence". The band's combination of the heaviness of metal and the speed of hardcore became known as “crossover”. Bands such as Corrosion Of Conformity, Dirty Rotten Imbeciles, and Cryptic Slaughter were all part of this new scene, but Katon W. De Pena's upper-range clean vocals stood out from the pack and HIRAX gained a fanatical following. HIRAX played regularly throughout the California Bay Area. "One of the best shows was when we played with Megadeth and Exciter," De Pena said. "As soon as HIRAX hit the stage, the whole club, 1,000 headbangers strong, went completely NUTS!!"

Drummer John Tabares was replaced with former D.R.I. drummer Eric Brecht and HIRAX released a second album for Metal Blade in 1986 titled "Hate, Fear, And Power”. The band had been through a lot by this time, constantly touring and several line-up changes, but they continued on. HIRAX released this mini LP because they were under pressure from the record label to put out a new product. “We weren’t their typical band so we stood out like a sore thumb,” De Pena said. “The record is only 22 minutes long and we probably confused even some of our fans at the time. We didn’t want to fit in. We wanted to do our own thing. We knew that we didn’t want to follow the satanic trends of the other metal bands at the time." It was the last release the band would record for Metal Blade. HIRAX soldiered on without any label support and released a 3-song demo titled "Blasted In Bangkok”. The '87 demo, which took only six hours to record and mix, was recorded the day after Katon's 23rd birthday. HIRAX was back to where they started, selling demos on their own, but now they had a loyal fan base behind them that had grown larger from the two Metal Blade releases. Because of these releases, the band would live forever in the hearts of true metalheads. Lautrec Records from Los Angeles, California released a 7" record of two songs from the "Blasted In Bangkok" demo.

That same year, Katon, along with drummer Gene Hoglan (Dark Angel, Death, Testament, and Strapping Young Lad), original Metallica bassist Ron McGovney, and guitarists Nathan Williams and Rodney Nicholson formed the band Phantasm and recorded a six-song demo with Bill Metoyer of Metal Blade Records. Phantasm toured briefly with Nuclear Assault and disbanded in 1988 because of power struggles between the members. The Phantasm demo finally got a proper release on Black Devil Records and Deep Six Records on the CD titled "Wreckage,” which also includes a show from the Phantasm / Nuclear Assault tour.

Disillusioned by the music industry, De Pena left HIRAX at the end of 1988 and Exodus front man Paul Baloff briefly replaced him. This line-up didn't last long and by 1989, HIRAX was no more. For the next 8 years, De Pena continued to support the underground, working at record labels and stores. He was never far from the music that he grew up with and played.