SAN ANTONIO — Bexar County authorities continue to search for a missing 29-year-old woman they say could have been a victim of foul play. 

According to officials with the Bexar County Sheriff's Office, Andreen Nicole McDonald never showed up to work Friday and did not return to her residence, located near Canyon Golf and Wilderness Oak. 

The missing 29-year-old stands at 5'11, weighs 160 lbs. and has black hair and brown eyes.

 Bexar County Sheriff Javier Salazar said no friends, family or business associates had seen or heard from McDonald since Thursday.

Salazar acknowledged that it was possible that McDonald had voluntarily left the country. However, McDonald left behind personal items that someone would normally take with them when traveling, which is why authorities believe she is missing under suspicious circumstances. 

In a Saturday evening update, Salazar said McDonald's husband, currently serving as a major in the U.S. Air Force, is a person of interest in the case. The sheriff said that when deputies made contact with him, "he quickly asserted his rights to legal counsel and refused to speak to us."

Later, authorities noticed the husband leaving the house on surveillance they placed around the property. He was later discovered to be in a gun shop, where Salazar said he purchased a handgun and ammunition. 

"(He) departed the store in a hurry; so much so that he left the gun he just purchased and his identification behind in the store." Salazar said. 

Deputies later detained him outside his residence "due to a possible mental issue." Because of his active status with the U.S. military, military investigators are also involved in the case, as well as FBI. 

Salazar also said they've obtained a second search warrant for the residence. 

"There is some blood evidence in this case that we're looking into," he added. 

The couple have a 6-year-old daughter, Salazar said, and she is currently OK and with other family members. 

The Sheriff's Office is asking that anyone with information on McDonald's whereabouts or interested in sharing surveillance footage from the 1000 block of Solitude Cove, call (210)-335-6000 or email missingpersons@bexar.org or bcsotips@bexar.org.