The killings of two real estate agents and robbery of a third within a week have agents in northeast Ohio on alert, and some are even cutting back on business as police warn them not to go alone to show properties.

One agent was found Monday strangled in a burning home that had been vacant and on the market. The next day, another was found shot once, also in vacant home up for sale. A third was threatened and robbed of her purse at gunpoint as she showed an apartment building Sept. 15.

Two brothers are charged in the robbery and are to be arraigned Thursday. Police are investigating whether the robbery is related to the first killing, and authorities said the investigation into the second death was focused on a person who is not one of the brothers.

"A lot of agents are really scared and upset," said Suzanne Brown, an office coordinator at RE/MAX Valley Real Estate in Youngstown, where all 24 agents in her office have canceled open houses scheduled for this weekend. She said the office has stopped taking on new clients until police are confident that all suspects are in custody.

Brown is reminding agents to take standard precautions when showing homes, such as following the prospective buyer into the property and not bending down or turning your back to the clients. Agents are also encouraged to meet new clients at the office, get identification and verify that they are preapproved for loans, all to help ensure that the potential buyers are serious and credible.

The agent who was robbed was showing a vacant apartment building in Boardman Township, outside Youngstown. She was told she'd be killed if she called police, Boardman police Capt. Donald Hawkins said. Her name was not released.

Paul Brooks, 27, and Robert Brooks, 25, were charged with aggravated robbery. They were being held in the Mahoning County jail, Hawkins said. It wasn't immediately clear whether either had an attorney.

Vivian Martin, 67, was found dead Monday on the kitchen floor of a burning home in Youngstown, according to police chief Jimmy Hughes. She was strangled, and authorities said the fire was arson.

The body of 51-year-old Andrew VonStein was found Tuesday in a vacant ranch-style house he was trying to sell about 40 miles west of Youngstown in a lakefront community near Kent State University.

VonStein, a prominent real estate agent who had worked in the Kent area for 32 years, was reported missing by his family when he failed to come home from work Monday night.

Police tracked VonStein, of nearby Ravenna, using a device in his car parked outside the tidy ranch home, which sits on half an acre of tree-shaded land with a swimming pool. Property records show the home, which sits across the street from a lake, is worth about $235,000.

At VonStein's home, his two grown daughters cried as they remembered him.

Brooke VonStein said her parents had returned from a vacation in Georgia on Saturday night.

"He went to work on Monday and never came home," she said.

VonStein often worked seven days a week, sometimes even selling houses while he was on vacation, his daughter said. He was active in the community and, for years, had been named the county's real estate agent of the year.

"It's just the oddest thing," said Judy VonStein, his sister-in-law. "The oddest thing. To know how much he is loved, that anybody would do this is very hard to understand."

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Sheeran reported from Cleveland. Associated Press Writer Matt Leingang in Columbus contributed to this report.

(This version CORRECTS Corrects typo in 1st paragraph. AP Video.)