KENT, Ohio — The killings of two real estate agents and robbery of a third within a week have agents on 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.

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.

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 near Kent State University.