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As New York City police continue to search for clues in the deadly shooting near Manhattan's Empire State Building, a police source says it appears the alleged gunman knew he would not be returning home.

The Wall Street Journal reports detectives on Sunday returned to the Upper East Side apartment of the laid-off clothing designer who allegedly gunned down a former colleague near the Empire State Building before being fatally shot by officers Friday. A law-enforcement official told the paper investigators removed a computer and "personal paperwork" from the apartment of 58-year-old Jeffrey Johnson.

Authorities say Mr. Johnson fatally shot his co-worker, Steven Ercolino, 41, outside the company's office before being confronted by police, who then killed him. Nine bystanders were injured by police bullets, three of them remain in hospitals in stable condition.

Reuters reports Johnson left his apartment around 8:00 a.m. that morning apparently not planning to return.

"He left the keys in an envelope for the landlord with no intention of ever coming back," a police source familiar with the investigation told Reuters.

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A source also contested a report in the New York Post that Johnson was being evicted, but did say Johnson was forced out of his home, according to Reuters.

"It was not an eviction," the source told Reuters. "Johnson was on a sub-lease as a sub-tenant. The tenant informed Johnson he would have to leave during renovation of the apartment by the owner."

Detectives spent the weekend sifting through evidence from Mr. Johnson's apartment, the official said, adding that a report of their findings is expected to be released on Monday, according to the Wall Street Journal.

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