Minutes before he was gunned down by Ronald Troyke, Arvada policeman Gordon Beesley had been at the shooter’s apartment after a family report that the 59-year-old was “going to do something crazy,” investigators revealed.

Arvada police say they received the warning from Troyke’s brother at 12:49 p.m. Monday, about 45 minutes before the incident that killed Beesley, Troyke and bystander Johnny Hurley, who officers say intervened and shot the gunman before he died from mistaken police gunfire.

In less than 20 minutes, Beesley and another officer arrived at Troyke’s apartment near Olde Town in Arvada, but didn’t find him — apparently missing him by just minutes. Police got a call soon after of a man acting strangely near Olde Town, and Beesley headed out.

At 1:34 p.m., Beesley was hit by a pair of shotgun blasts fired by Troyke, who had run up behind the 19-year-veteran officer in an alley, records released by police show.

Arvada police release more details, video of deadly shooting

The warning was revealed after police released a video Friday of the incident recorded by a surveillance camera at a nearby business.

Police say Troyke, a loner who had little on his criminal record, also wrote a four-page letter before the shooting describing an apparent vendetta against police in general and the Arvada agency in particular.

“We the people were never your enemy, but we are now,” police say Troyke wrote “This is what you get, you are the people who are expendable.”

Officers haven’t revealed what drove Troyke’s alleged hatred. Sources have said Troyke had been seen at earlier police scenes recording the actions of officers.

After Troyke shot Beesley, police say he went back to his pickup parked nearby and grabbed a semi-automatic rifle before Hurley, armed with a pistol, fatally shot the gunman.

Police say a responding officer fired on Hurley when he spotted him holding Troyke’s rifle. Sources told the Gazette Hurley picked up the rifle to empty it of ammunition.

“The Arvada Police Department understands and appreciates the public’s interest in the events that resulted in the tragic loss of officer Gordon Beesley and the hero Johnny Hurley,” the department said on Facebook. “We want to be clear that although these two deaths unfolded as part of the same incident, they are being investigated separately.”

Arvada police release video of shooting in Olde Town

Hurley’s death is being investigated by outside agencies in a team led by the 1st Judicial District Attorney Alexis King.

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King hasn’t said when that investigation will be completed and has released few details on what it has already revealed.

The officer who shot Hurley, whose name wasn’t released, was placed on paid administrative leave pending the outcome of the investigation, the department said.