A man in Austin, Tex., was killed and six other people injured on Wednesday in what the authorities were investigating as a chemical suicide in a housing complex near the University of Texas.

The authorities said they responded to a call at 2:30 p.m. of a man in cardiac arrest at 911 West 21st Street, an off-campus apartment complex.

When firefighters arrived they found a “Keep Out” sign outside the apartment door and another sign on a closet indicating the presence of hydrogen sulfide gas, said Lt. Kevin Haas of the Austin Fire Department. Hydrogen sulfide is a very poisonous gas with the odor of rotten eggs.

The man, who was in his 20s, was removed from the closet and taken outside. Resuscitation efforts lasted for an hour, and he was pronounced dead at the scene, said Cmdr. Mike Benavides of the Austin-Travis County Emergency Medical Services.