(CNN) -- Wall Street Journal reporter David Bird left his New Jersey home Saturday evening, hoping to take a quick walk before it rained. He hasn't been seen since.
For the past several days, authorities and dozens of volunteers have been scouring the area around Bird's Long Hill home to find the missing 55-year-old father of two, who was known to walk the trails around his house.
Bird was a recipient of a liver transplant nine years ago and requires medication twice a day, his sister-in-law Chris Fleming said.
"We have every reason to believe that he just wanted to go for a little stroll," longtime family friend Jacquie Petras told CNN affiliate News 12 New Jersey. "There's nothing pointing to anything else."
Bird is an energy markets reporter at the Wall Street Journal. Fleming described him as a great guy who wrote a letter to the family of his liver donor every year.
"He felt very thankful to the donor family for giving him his life that their loved one allowed him to live," Fleming said. "Life was a gift, and he was very, very grateful."
The investigation is being handled by the local police and prosecutor's officer as well as the FBI.
Wall Street Journal managing editor Gerard Baker called Bird a "longtime member of the Dow Jones newsroom."
"Our thoughts are with his family and we are working with the Long Hill Township Police Department as they continue their search."
Media reports have said that Bird's credit card was reportedly used Wednesday in Mexico, but Fleming said the family is baffled by these reports. Police are still following up on any and all leads, Fleming added.
"There is nothing in his background that shows any indiscretions," Chief Michael Mazzeo of the Long Hill Township Police Department told CNN affiliate WABC.
Residents around Long Hill have been asked by police to check their properties for signs of Bird, in case he sought protection from the rainy weekend weather.
"It just doesn't seem real," Fleming said. "We just want to bring him home."
CNN's Elizabeth Landers and Jacqueline Rose contributed to this report.