He spoke to his wife by phone for a few minutes at 8:30. Colleen says she was at the grocery store during that call (the couple had no children) and asked him if he needed anything.
Her husband, who would be dead in about two hours, requested chocolate pudding.
As noted, Drenth visited Officer Aaron Lentz at the homeless shelter twice that night. The barricade call interrupted the first visit, and his return visit of about 40 minutes began about 8:50.
The sergeant then returned to patrol, again based on GPS readings and videotape from cameras mounted on state buildings west of 15th Avenue and south of Washington Street.
Over the next hour or so, Drenth shined his car searchlight at locations west of Seventh Avenue and south of Washington, not far from where he died.
He drove slowly, stopping occasionally for a minute or two as he traversed the mostly non-residential area.
"He engaged in behavior that is consistent with routine police work," a Phoenix PD investigator wrote later.
"After ending the [9:59 p.m.] cell-phone conversation with his wife, Drenth appears to be actively patrolling an area known for criminal activity . . . While it is possible to see his vehicle [on some cameras], it is not possible to determine if there was anyone else in the vehicle with him."
One camera momentarily picked up Drenth's patrol car at 10:25 p.m. traveling south near the alley at 18th and Jackson. Its headlights were off, not unusual when an officer is on patrol.
Also at 10:25, the sergeant engaged the "subject stop" screen on his control monitor. The push of a button enables officers to enter information about a potential suspect.
But the sergeant apparently never typed in anything, adding to the intrigue.
Citing GPS data, a police report says Drenth's car was "relatively stationary" for 40 seconds near the volleyball court before it headed to the rear of the alley at 10:26 p.m.
The car wasn't seen again until Capitol Police assistant Steve Vernier spotted it a half-hour later.
But investigators learned that the cameras would not have detected the sergeant's car in the alley had he not touched his brakes as he drove into it.
Detective Brewer confirms that other vehicles or anyone on foot could have entered and left the alley without getting detected by the nearest camera.
It's unknown whether Drenth picked up someone for a pre-planned meeting or what he may have been up to at that critical moment.
By the time he stopped at the end of the alley, he officially had been incommunicado for about an hour.
Sometime within 28 minutes after he parked his patrol car, Sergeant Sean Drenth died violently.
The homicide investigators continued their work into the late morning, even after more than 10 hours at the scene.
Among the findings were 93 latent fingerprints on Sean Drenth's patrol car and 53 sets of footprints belonging to police officers, many whom had rushed into the crime scene.
Of possible significance, crime-scene specialists found the footprint of an unknown person on a notebook binder on the front floorboard inside Drenth's vehicle.
The print did not come from footwear that Drenth or any other on-duty officer would have been wearing.
Investigators also collected unidentified DNA from somewhere inside the scene that Phoenix PD never publicly revealed.
Detective Brewer says his initial feeling that night was that Sean Drenth had been murdered.
"If there's a person on this department who's killing people, I want to know about it," Brewer says. "So a cop kills him? Why does he want to kill him? There needs to be a motive.
The attorney general [case]? Could be. But is that enough for another officer to kill Sean?"
Lieutenant Joe Knott, says: "We researched [the off-duty case] well enough, I think, to establish that there is no link. We found nothing to indicate that any of those people were involved."
New Times spoke extensively about the case with Scottsdale forensic psychiatrist Steven Pitt, who has consulted with the Phoenix PD on several cases, though not on Drenth.
"At the end of the day," Dr. Pitt says, "we are dealing with either an incompetent or incomplete investigation by the Phoenix police and/or falsehoods promulgated by the Drenth camp.
"The Drenth camp wants you to believe that Sean was a saint, and the police want you believe that they have done a thorough investigation. It can't be."
As for the ultimate question, Pitt says, "I'm not impressed with the data that supports this being a suicide. Suicide runs counter to everything we know about this officer. But the police just scratched the surface of the psychological 'autopsy' that should have been done on Sean — and still should be done."