Police Suspect 'Serial Bomber' in Deadly Austin Attacks The suspicion comes after the city was hit Sunday by its fourth explosion in a month Austin Interim Police Chief Brian Manley. Austin Interim Police Chief Brian Manley. According to authorities, the last explosion may have been activated by a tripwire, which shows
"a higher level of sophistication, a higher level of skill." Two men in their 20s were injured in the attack. Investigators have yet to establish a motive behind the attacks.