SAN ANTONIO – The search for a missing 29-year-old mother, wife and local business owner has taken a grim turn.

Bexar County Sheriff Javier Salazar said authorities presume Andreen McDonald to be dead and are now treating the investigation as a body recovery.

"There is more evidence than not that Ms. McDonald has been killed," Salazar said.

Authorities arrested McDonald's husband, Andre McDonald, in connection with her disappearance Sunday afternoon. He is charged with tampering with evidence, according to authorities.

The announcement comes after investigators served a search warrant Saturday night at McDonald's home near Canyon Golf and Wilderness Oak in far north Bexar County, which she shared with her husband, a major in the U.S. Air Force, and their 6-year-old daughter. Authorities said that the warrant was obtained when investigators uncovered blood evidence, as well as "new evidence in plain view."

Deputies first detained McDonald's husband Saturday afternoon, citing mental health concerns.

Authorities said they set up surveillance on the McDonalds' home and covertly followed Andre McDonald to a gun shop Saturday afternoon, where they said he hurriedly purchased a firearm and ammunition. According to Salazar, McDonald was in such a hurry, he left behind the firearm he had just purchased and his ID.

"At that point, we were not certain if there were some suicidal thoughts going through the subject's mind," Salazar said. "(Deputies) made contact with him outside the residence, took him into custody, detained him at that point due to a possible mental health issue."

Authorities said McDonald is considered a suspect in his wife's disappearance and are building a "criminal case."

"We do suspect a crime has been committed and (Andre McDonald) is our only person of interest that we are looking at," Salazar said.

Salazar said Saturday night that the FBI and the military's Office of Special Investigations joined the investigation into Andreen McDonald's death. Authorities spent Saturday scouring the couple's home and vehicles and asked the public to alert authorities if they had seen any of the couple's four vehicles "in a remote area or driving suspiciously in a wooded area."

Friends reported McDonald missing after they went to her home to try and locate her and instead encountered her husband, the sheriff said.

According to Salazar, McDonald's friends told deputies that they were unable to get answers from McDonald's husband as to where she was.

"We weren't able to get much information (about McDonald's whereabouts), either," Salazar said early in the investigation. "In fact, Mr. McDonald asserted his rights and retained the use of an attorney, so we have not been able to speak to Mr. McDonald very much as a result of this."

Salazar immediately described McDonald's disappearance as "very suspicious" after investigators recovered her purse, wallet, car keys and "anything that, typically, you would expect somebody to take with them if they were going to be leaving," Salazar said.

(Image via BCSO)

They said they have not yet talked to the couple's 6-year-old daughter, as she is autistic and mostly nonverbal.

Friends of the 29-year-old tell KSAT that it's unfathomable that McDonald would abandon her daughter and successful home health care businesses. McDonald was last seen Thursday, the sheriff said.

BCSO officials are asking for anyone with information on Andreen McDonald's disappearance to call the Sheriff's Office at 210-335-6070 or email missingpersons@bexar.org or bcsotips@bexar.org.