Major Nidal Hasan seemed worried about the results of an HIV blood test taken a week before the Fort Hood shooting rampage, according to federal investigators piecing together background details on Hasan's life.

The suspected gunman in the massacre at Fort Hood, Texas, Nov. 5, 2009, was identified by ABC News as Army Maj. Nidal Malik Hasan. He appears here in a Defense Department photograph.

(Handout)

The information came from a member of the Fort Hood medical staff who was in the building where Hasan is accused of opening fire on November 5 and killing 13 people.

The investigators said there was no indication that Hasan was HIV positive, although a bottle of medicine used to treat HIV-positive individuals, Combivir, was seen in Hasan's apartment by ABC News last week. Medical experts say many doctors also have Combivir on hand in case of an accidental needle stick. A second drug seen in the apartment, clarithromycin, is an antibiotic designed to treat respiratory infections. However, it can also be used to treat specific opportunistic infections in patients with HIV.

Hasan, who is not married, was a regular at a Killeen, Texas strip club which features nude dancers, according to employees there.