An explosion at a South Austin Goodwill store on Tuesday evening injured a man in his thirties, according to Austin-Travis County Emergency Management Services. Austin police said the sixth blast in the Capital City this month was not a package bomb, but an incendiary device described as “an artillery simulator.”

“At this time there is no reason to believe this incident is related to previous package bombs,” police tweeted just after 8 p.m. Austin Assistant Police Chief Ely Reyes said the incident occurred just after seven Tuesday evening, when a Goodwill employee handled one of two of these simulators “that looks like some type of ordnance or some type of momento,” causing one to go off in his hand.

“We have no reason to believe that this was an attempt at a copycat,” Reyes said during a briefing Tuesday night.

But the massive emergency response, including the evacuation of a nearby grocery story and the “reverse” evacuation of a nearby high school (people were ordered into the building) demonstrated the growing angst that residents of the city are starting to face.

This was the area’s second explosion on Tuesday, part of a string of bombings that have killed two and injured four across Austin and in Schertz, northeast of San Antonio. Investigators said earlier Tuesday that the five previous bombs are connected.

Officials said the explosion happened on Brodie Lane near West Slaughter in far South Austin, about eight miles from Sunday’s blast in Southwest Austin.

The sixth explosion extends what has already been a tense day for residents and first responders in Austin. Early Monday morning, a bomb disguised as a package exploded at a FedEx facility in Schertz; there were no serious injuries. Investigators later found an undetonated bomb disguised as a package at a FedEx store near the Austin-Bergstrom International Airport in Southeast Austin, and confirmed that a package delivery store in Sunset Valley is believed to be the source of the bomb that exploded in Schertz. FedEx has cooperated with authorities and turned over to investigators information on the sender of the package, offering a glimmer of hope that the police and federal investigators who have struggled to find any clues leading to a suspect or motive may finally have something to work with.

Tuesday’s explosions came two days after a trip wire triggered a bomb that injured two men in Southwest Austin. On March 12, two separate packages exploded, one killing 17-year-old Draylen Mason and injuring his mother at their East Austin home, and the other injuring 75-year-old Esperanza Herrera in Southeast Austin. Anthony Stephan House was killed on March 2 when a package exploded at his home in Northeast Austin. Austin police chief Brian Manley has described the bombings as the work of a serial bomber.