Ransom, 30, pleaded guilty to aggravated manslaughter and robbery in connection with the February 12, 2019, fatal shooting of Simonsen.
"The defendant set in motion a terrible chain of events that began with a robbery and ended in a spray of bullets when Ransom pointed what appeared to be a deadly firearm toward police officers. The defendant was repeatedly told to lower his weapon but did not do so. The heartbreaking result was the loss of Detective Simonsen's life and Sergeant Matthew Gorman being shot in the leg. We express our condolences once again to Detective Simonsen's family and hope today brings them a measure of closure," said Melinda Katz, Queens District Attorney.
He also pleaded guilty to robbery in the second degree for a separate robbery on February 8, 2019.
Based on the negotiated plea, Justice Holder is expected to sentence Ransom to a total of 33 years in prison to be followed by five years post release supervision at sentencing on November 17, 2021.
(Video in media player from report on Ransom in 2019)
Ransom and an accomplice, Jagger Freeman, used a fake gun to hold up a T-Mobile store in Richmond Hill, Queens. When police arrived, Ransom ran towards them pointing the fake weapon.
Officers opened fire from both sides of the store and the 42-year-old Simonsen was struck and killed.
Sergeant Matthew Gorman was seriously injured with a bullet wound to his left leg.
Ransom was shot eight times but survived.
Ransom and Freeman had requested a release from Rikers Island due to COVID-19 concerns one year ago, but the judge denied their request.
WATCH: Jagger Freeman being led out of the police precinct with fallen Detective Brian Simonsen's handcuffs:
Second suspect arrested in connection with robbery that led to NYPD Detective's friendly-fire death
ALSO READ: Simonsen's widow talks about his life one year after his death
Widow of fallen NYPD Det. Brian Simonsen reflects on life one year later
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