Two days after a deadly mass shooting inside 345 Park Avenue, the entrance to the Midtown office tower is now barricaded, with NYPD officers standing guard. Employees of the building are continuing to work remotely as the investigation moves forward.

Police say 27-year-old Shane Tamura drove from Las Vegas to Manhattan with two rifles, extra ammunition and medication in his car. Surveillance video shows him stepping out of a BMW Monday night with an M4-style rifle before walking straight into the lobby and opening fire.

Tamura killed four people — including off-duty NYPD Officer Didarul Islam, building security guard Aland Etienne and Blackstone executive Wesley LePatner — and injured a fifth person before shooting himself on the 33rd floor.

Investigators say Tamura left a handwritten suicide note in his pocket claiming he suffered from chronic traumatic encephalopathy, or CTE, a brain disease linked to repeated head injuries. He only played high school football, but he blamed the NFL for his mental health struggles. Doctors note that CTE can only be diagnosed after death.

NYPD detectives are now in Las Vegas, where they are visiting the gun store where Tamura legally bought a revolver last month. They are also questioning the person who provided him with the parts to assemble the rifle used in the attack.

For the people who worked in the building, the tragedy feels deeply personal. Allen Hodge, who works in corporate dining inside the tower, says he knew both Aland Etienne and Wesley LePatner well.

“Yes, I've been working in this building here for about 10 years now. I work for Wesley personally. Every morning I talk to her, I go get a coffee, I go get a water. I set up all the events, as well as all the meetings for the 24th, 25th and 26th floor here. It’s overwhelming just to hear about it, see it and know that. I know them personally. I know Al personally as well, but you know, I'm sorry for all the losses that actually happened, including the police officer, but it seems like nobody is talking about my friends. And like I said, I know them personally. I deal with them every day, and it seems like nobody's talking about my friends.”

Hodge says his department is now on leave until further notice.