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Here's a modern twist on an old defense: The app made him do it.

The Uber driver charged with killing six people and wounding two in Kalamazoo, Michigan, last month told detectives that the car service’s mobile phone application turned him into "a puppet" and that he wasn’t sure "how much he had or had not done."

According to police documents released Monday, Jason Dalton, 45, told detectives during an often muddled Feb. 22 interview that he is "not a killer and he knows that he has killed. Dalton said that he could only tell us that [the app] has the ability to take you over."

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Dalton also appeared to blame the app for making him wear a bullet-proof vest during the Feb. 19 shooting spree, according to the documents.

When a detective asked him why "the system" allowed him to stop for the police officers who arrested him several hours after the spree began, "he said he didn’t know," the documents say.

"Dalton told us that literally when logged onto the site (referring to the Uber app) it started making him be like a puppet," the documents say.

In an incident report also released Monday, one of the arresting officers said that when he first approached Dalton, the suspect "proceeded to reach back to his right side." The officer stopped him, and during a subsequent search, discovered a 9-mm pistol in Dalton’s right pocket.

"His demeanor was not normal as he stared blankly ahead and did not respond to any questions," the report states.

Related: 14-Year-Old Shooting Victim Remembers Man With a Gun

The revelations came on the same day that authorities released audio of 911 calls describing the shootings and dash-cam video that showed his arrest.

The documents also contain an interview with a former colleague at Progressive Insurance who said Dalton had a fiery temper and "a side that many people may have not seen unless they worked with him."

The former colleague said that he had seen Dalton yell at customers, slam the phone and get angry and defensive when someone complained about his demeanor. Dalton, the colleague said, "did not seem to have any conflict resolution skills."