The man who killed 25-year-old Indian student Sharath Koppu in Kansas City had an extensive criminal background and was just 15 when he was first arrested, according to a media report.

Marlin James Mack, 25, who was shot dead, July 15, after shooting three Kansas City police officers, was first arrested in Tulsa, Oklahoma, when he was 15 for breaking into cars and two years later he was held again for bringing a gun to school, the Kansas City Starreported.

At 17, he was sentenced to prison for five years for robbing a woman at gunpoint in front of her three small children.

Though Mack was once known as one of Tulsa’s most wanted robbers, Kansas City police were not aware of him before he became the lead suspect in the killing of Koppu, who hailed from Telangana.

Koppu, a University of Missouri-Kansas City student, was fatally shot on July 6 in the back during a suspected attempted robbery at a restaurant where he worked in Missouri.

At age 17 he (Mack) was pretty much a liar and misfit extraordinaire, David Walker of the Tulsa Police Department, who had interviewed Mack in 2011, told the daily.

For his first arrest, in 2009, Mack was charged with robbery by force.

Despite Mack’s young age, he already had a reputation for violence, the daily said quoting the police officer.

He was sentenced to five years in prison for second-degree robbery, possession of a firearm as a juvenile and two counts of assault with a dangerous weapon.

In March 2015, Mack was released from prison. Just seven months later, he returned to prison for carrying a firearm after a former conviction of a felony. He was released in February 2017.

Despite his extensive criminal record in Oklahoma, he had never come to the attention of Kansas City police. He became a person of interest in the shooting death of Koppu, a software engineer who had come to the U.S. in January to pursue his master’s degree.

Mack’s father is serving a life sentence for shooting two people in the head in 2000.