CHICAGO (CBS) — He warned us.

For days, Jason Nightengale drove around Chicago, telling his Facebook Live audience he was going to kill people – and even blow up his whole community.

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He also flashed his gun on video.

On Saturday, police said Nightengale killed three people and injured four more in a shooting spree from the South Side to Evanston. On Monday night, CBS 2’s Jermont Terry looked into possible missed warning signs.

For several days – including the very day of the rampage – Nightengale was seen ranting on Facebook. He talked about his intentions to hurt people.

Police said over a period of several hours Saturday, Nightengale made good on his threats. They said he shot and killed University of Chicago graduate student Yiran Fan, 30, and doorwoman Aisha Johnson, 46, in two buildings in the Indian Village District in the East Hyde Park-Kenwood community, and then shot and killed Anthony Faulkner Jr., 20, in a convenience store at 9307 S. Halsted St.

He also shot and wounded a 77-year-old woman in the building foyer with Johnson, an 81-year-old woman working at the convenience store, a 15-year-old girl in a car in the 10300 block of South Halsted Street, and another woman he took hostage in an IHOP at Howard Street and Asbury Avenue in Evanston after heading many miles there, police said.

Days later, there were questions about why it took so long to catch Nightengale as he traveled around randomly shooting people with an itinerary that spread so far.

“There are different reasons for people engaging in violent behavior,” said Loyola University Chicago professor of psychology and criminal behavior Arthur Lurigio.

Lurigio said many may have seen the accused gunman’s rants, but that may not have translated for people into cause to take action.

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“Just viewing someone behaving in a threatening manner on Facebook or some other social platform isn’t likely to provide you with enough information to make a plausible risk assessment about the likelihood that they would commit future violence – especially if you’re not a trained professional,” he said.

But Lurigio added that if a loved one saw Nightengale’s videos, then preventative action possibly could have been taken.

“Unless I had a personal relationship and I’ve known him for years and I can conclude this is very uncharacteristic – this is a very serious, although ambiguous, threat – this needs to be followed up upon,” Lurigio said.

Nightengale’s family refused to talk to CBS 2, and only said “they’re sorry,” but would not elaborate.

We do not know if anyone called authorities to report the posts where he clearly talked about carrying out acts and showed weapons. But Lurigio said it was a broad threat – making it harder.

“The anger being expressed by this young man seem much more ambiguous; more of a general expression of rage,” he said.

A motive into the deadly rampage was not known Monday night. But Lurigio points out people should not be quick to blame mental illness alone – saying crimes like this are rarely linked solely to mental problems.

We may never know the motive, since Nightengale was killed by police.

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