A man who was shot dead by an undercover officer after a bank robbery in Phoenix on Saturday was behind the murder of a cop last week, authorities say.

40-year old Mario Edward Garnett began a spree earlier this month in Atlanta, attempting a bank robbery but resorting to holding up a customer at the ATM; several hours later, he showed up in Mississippi, where he robbed another bank and was very nearly caught. The robbery ended in a violent gunfight, during which he shot two police officers. Gale Stauffer later died from his injuries.

Garnett’s robbery in Phoenix was almost successful, but he ran into a police officer during his getaway and opened fire. The officer wasn’t wounded, and an undercover agent who happened to be nearby on an unrelated case was able to intervene.

“This is a situation where we had a detective on the street doing a follow-up on an unrelated incident who heard a radio call. He was close by, so he responded,” Phoenix Police spokesman James Holmes said. “It chills me to think what might have happened had he not responded, based on the information we have now.”

Officer Stauffer was laid to rest on Friday with thousands in attendance; Officer Joseph Maher has been upgraded from critical condition and is able to walk with some assistance.

Garnett, it turns out, had just been released from an eight-month prisons sentence in July after a 2010 incident in which he wrote on the official White House website that he would shoot President Obama.

“If you order a strike on Iran, I’m going to come up there and blow your brains out on national TV,” he wrote.

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