At just 27 years old, he already has a long rap sheet. When he was 18, Cowell's adult criminal record included misdemeanor drug offenses, obstruction of a peace officer and assault. On the assault charge, Cowell was convicted and released on probation.
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When he was 22, Cowell was convicted of battery. Two years later, in 2015, he had another conviction for using drugs.
VIDEO: 'Remember Her' A tribute to Nia Wilson
'Remember Her' A tribute to Nia Wilson
Then in 2016, there were more misdemeanor charges -- this time at the Target store in Contra Costa County. Cowell was caught shoplifting and carrying drug paraphernalia.
Contra Costa County DA spokesperson Scott Alonso says police also found him with this: "I believe he had a tear gas canister. So a wide variety of charges in that one, all misdemeanors."
In May 2016 was Cowell's most serious crime - second degree robbery at Lucky's in El Cerrito. Cowell was known to be a shoplifter here but this time, he was caught in the act. "The loss prevention officer attempted to confront him, detain him and that's when the defendant reacted with a gun, a handgun," Alonso told ABC7 News.
VIDEO: This is the moment the BART stabbing suspect was arrested
This is the moment the BART stabbing suspect was arrested
It turned out to be a toy gun, but he also had a boxcutter -- a real weapon. Cowell ran from the store and police caught him at the El Cerrito Plaza BART station.
"Our prosecutors sought that felony charge. And he was ultimately sentenced to state prison for two years in October of 2016," Alonso said.
VIDEO: What we know about the deadly Oakland BART stabbing
What we know about deadly stabbing at Oakland's MacArthur BART station
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Cowell completed his sentence and was paroled out in May 2018.
He also has a record in Contra Costa's Civil Courts.
In 2015, a Concord woman filed a restraining order against him. The following year, there was another restraining order. This one from Kaiser Hospital in Richmond, stating he had repeatedly threatened staff members.
RELATED: Mugshot released of MacArthur BART station stabbing suspect
You may be wondering -- what about his mental state?
Alonso says, " He was evaluated by a doctor in the robbery case in 2016. He was found competent to stand trial."
Cowell also has several misdemeanor offenses in Alameda County -- petty thefts, vandalism and drug use.
BART authorities tell ABC7news that Cowell has deep ties to North Concord. He has tattoos on his body, which highlight those ties. One says "North Concord." Another on his neck reads "925," the area code for Concord and incidentally,a tattoo the tipster told police about when he called them. That was the tip that led to his arrest.
Go here for full coverage on the stabbing at Oakland's MacArthur BART station that took the life of 18-year-old Nia Wilson.
CONTINUING COVERAGE ON DEADLY BART STABBING:
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- What we know about deadly stabbing at Oakland's MacArthur BART station
- 'Remember Her' A tribute to Nia Wilson
- Here's how you can help the family of BART stabbing victim Nia Wilson
- Chilling dispatch call describes terrifying fatal MacArthur BART stabbing
- 'He was wiping off his knife': BART stabbing victim recalls horrific attack that killed sister
- Heartbroken father demands justice after daughter stabbed at BART station
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- Bart releases info on pair of homicides