PFLUGERVILLE, Texas — As a SWAT team closed in, the suspected bomber whose deadly explosives terrorized Austin for three weeks used one of his own devices to blow himself up. But police warned that he could have planted more bombs before his death, and they cautioned the city to stay on guard.

Mark Anthony Conditt, an unemployed college dropout who bought bomb-making materials at Home Depot, was tracked down using store surveillance video, cellphone signals and witness accounts of a customer shipping packages in a disguise that included a blond wig and gloves. His motive remained a mystery.

Police finally found the 23-year-old early Wednesday at a hotel in a suburb north of Austin known as the scene for filming portions of “Friday Night Lights.” Officers prepared to move in for an arrest. When the suspect’s sport utility vehicle began to drive away, they followed.

Conditt ran into a ditch on the side of the road, and SWAT officers approached, banging on his window. Within seconds, the suspect had detonated a bomb inside his vehicle, blasting the officers backward, Austin Police Chief Brian Manley said.

One officer then fired his weapon at Conditt, the chief said. The medical examiner has not finalized the cause of death, but the bomb caused “significant” injuries, he said.

Police discovered a 25-minute video recording on a cellphone found with Conditt, which Manley said he considers a “confession” to the bombings. It described in great detail the differences among the bombs, he said, but no motive.