KIMA learned this investigation is the second involving a policy violation. Those details aren't public.
And now witnesses claim he was supposed to be undercover on a drug bust but ended up at a cheap motel with an 18-year-old girl.
>>Documents: Click here to read YPD's 99-page internal investigation
As an officer of the law Hildebrand is paid to pull gang bangers and other criminals off the streets. But witnesses say this was not why he picked up a girl walking along North 1st Street back in May of 2011.
"He's supposed to be here to protect people, not take girls to a motel room."
Yakima Police documents obtained by KIMA said Sgt. Hildebrand was working his shift when he says he saw "a prettier girl than you would see walking."
The internal report indicates Hildebrand says the 18-year-old told him she was being circled by a car, so he offered her a ride. He told investigators that as he drove her home, she told him she was a drug addict.
Hildebrand explained to Lt. Tom Foley, who handled the questioning, that he figured she'd be useful in an undercover bust.
The report states plans were made to take her to a hotel room for a sting, and that he used his credentials with law enforcement to get a free room.
Action News spoke to the person on duty at the Yakima Inn that day. She didn't want to be identified.
Reporter: "So when he came here, he asked for a room in the back, specifically?
Hotel employee: "Yeah."
Reporter: "Was that weird?
Hotel employee: "Yes."
The Yakima Inn had been used for stings before but never like this. Workers said officers usually come in a group and dressed in uniform.
The motel employee told police and KIMA that Hildebrand was in plain clothes and by himself. She says she watched the Sergeant later return with the girl and go to the room.
"He no come outside, he no open the window," said the hotel employee. "And I say, 'he's working, or he's waiting for more cops?'"
After two hours the worker said no other cops came to the Yakima Inn.
Reporter: "So the window was closed like this?
Hotel employee: "Yes."
Reporter: "Pretty hard to do undercover work when you can't see out."
The employee told police the sheets were left tussled.
Sgt. Hildebrand told internal investigators he was in the room for 15 minutes and left the bed untouched. He explained to Lt. Foley that the sting never went down because the girl couldn't get the drugs.
A woman claims she saw the girl shortly after her visit with Hildebrand.
"She came back with money," the witness said. "She didn't have money when she left. She was pretty intoxicated. So I don't know what went on, but why would she have money, you know? Why would he give her money, just to give her money?"
Reporter: "Were they boyfriend, girlfriend?"
Witness: "I don't know."
Police never found evidence to confirm exactly what happened that night at the Yakima Inn. But he was out of touch with the department for more than two hours which is a violation of YPD policy.
Sgt. Hildebrand got a written reprimand.
The girl was never found by police. It's believed she left town and took the story of that night along with her.
To keep the story balanced Action News reached out to Yakima Police and Sgt. Hildebrand for comment. Neither was able to speak to what happened last year due to a separate, ongoing internal investigation.
In the meantime, KIMA filed a public records request for documents related to the latest investigation.