Manhattan shooting victim's dad had a stroke when he learned his son was killed

The father of an NYPD officer killed in a mass shooting at a Manhattan office towerhas suffered a stroke after being told of his son's murder.

Didarul Islam, 33, was working in security at 345 Park Avenue on Monday when he was gunned down by 27-year-old Shane Tamura during the shooting that killed four people. The tragedy has left Islam's family in pieces.

"His father went last night to see him," Islam's cousin Muhammad Mainul Islam said. "When he heard the message, he had a stroke, feeling bad. So he had a stroke so the hospital did not release him."

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Islam's pregnant wife was also rushed to hospital after becoming overwhelmed with grief. "They are all crying," Islam's cousin added. "There is no brother, only him. The family is really feeling a big problem. His wife had the doctor’s appointment. I heard one police officer from the precinct, she took [her] to the hospital."

Islam, a father of two, had emigrated from Bangladesh and served in the NYPD for three years. He was one of three people killed in the building's lobby after Tamura entered the skyscraper and opened fire. The other victims were named as Blackstone executive Wesley LePatner, security guard Aland Etienne, and Julia Hyman, who worked for Rudin Management.

Tamura then took the lift to the 33rd floor, where he shot and killed another woman before turning the gun on himself. Police believe he had been targeting the NFL's offices, but ended up on the wrong floor. The tower, owned by the Rudin family - a powerful force in New York real estate - is home to tenants including the NFL and global investment firm Blackstone.

It is not yet clear what Tamura's motive was for the massacre, but a letter was found on his body suggesting he had grievances with the NFL and its handling of chronic traumatic encephalopathy (CTE).

"Terry Long football gave me CTE and it caused me to drink a gallon of antifreeze," the shooter wrote, according to the source. "You can’t go against the NFL, they'll squash you." He continued in the note: "CTE chronic traumatic encephalopathy. Study my brain please I’m sorry Tell Rick I’m sorry for everything."