Officials say they will also investigate whether warning signs about Major Hasan's behavior were ignored.

VOA: special.2009.11.14

In addition to monitoring their own behavior, employees and managers should be trained and encouraged to watch for warning signs in others.

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Rather, Keys tweeted a copy of a "final written warning" he said he received from Reuters in October, which admonished him for unprofessional behavior after he mocked a Google executive from a fake Twitter account.

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The warning first came from an imam in Toronto, who in turn was tipped off by suspicious behavior on the part of one of the suspect.

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