UPDATED 08/13/12 – 4:55 p.m.

CHICAGO (CBS) — A woman was found slain Monday at the tony Whitehall Hotel just off the Magnificent Mile, and police were conducting a homicide investigation.

Police say the woman — who is 22 and is from Dallas, Texas — was found unresponsive in her room in the hotel, at 105 E. Delaware Pl., around 10 a.m. Monday.

Fire officials tell CBS 2 the woman had suffered head trauma and was dead at the scene.

A source told WBBM Newsradio’s Steve Miller the woman was apparently shot in the head.

Police were conducting a homicide investigation Monday afternoon.

CBS 2′s Mai Martinez reports most of the hotel guests thought someone famous was staying at the hotel because of all the police and media presence. As you can imagine, they were shocked to learn a woman had been shot to death in a 7th floor room of the hotel.

Chicago police spent much of the day carrying evidence bags into and out of the hotel – not exactly the sight hotel guests wanted to see.

Whitehall guest Kevin Darby said, “I just walked down, and three police officers walked in, and headed to the elevator.”

As police investigated the woman’s death, many hotel guests tried to remember if they had seen or heard anything strange.

Carolyn Such and Maryetta Palmer said they wonder if what they thought was someone trying to get into their room early this morning might have been connected.

Such said, “It could have been a cleaning person. They seemed to have a key.”

Palmer said, “But they didn’t announce themselves, and they didn’t knock.”

Darby said he didn’t see or hear anything overnight.

“No, I was super tired, so I just … went to bed early. Didn’t hear anything,” he said.

But another hotel guest did. He was also on the 7th floor, just a few doors down from where the victim was discovered.

He didn’t want to talk on camera, but he told investigators he heard something like a gunshot around 3:15 a.m. Monday.

Knowing someone was found dead was too much for Darby.

“I’ll probably have to try to move hotels tonight,” he said.

It also raised concerns among those checking in on Monday.

“It’s a little bit scary, concerning. You know, you don’t want to stay anywhere where there’s violence like that,” said Brian Baugh. “I’m kind of speechless right now.”

Baugh said the hotel didn’t notify him about the woman who was killed there.

“No, I called earlier to see if our room was ready, and they said ‘Oh yeah, it’s ready for you,’” he said.

The Cook County Medical Examiner’s office was not releasing the victim’s identity, as of Monday afternoon, pending notification of her family. They would only confirm she’s a 22-year-old woman from Dallas.

The Whitehall is a high-end boutique hotel with 222 rooms, and has been in operation since 1927.