MIDTOWN, Manhattan (WABC) -- The NFL is implementing new safety protocols across the league in the wake of last month's deadly mass shooting at a building in Manhattan.

Until last month, the NFL headquarters was part of a typical, and well-known high-rise office building in Midtown Manhattan. Now, it's part of a stronghold of security after a shooter walked in and killed four people inside the building before killing himself.

A lot has changed inside 345 Park Ave . in the weeks since then. Gun-detecting K9's and a noticeable security presence await all who enter the building, the same doors Shane Tamura entered with an assault rifle and a desire, investigators believe, to target NFL headquarters.

September 4 is opening day for the NFL, so things are heightened right now.

Taking pr

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