Austin Police Chief Brian Manley said the APD and the USPS will work with the Federal Bureau of Investigation and ATF National Response Team along with other agencies to investigate and they will "leave no stone unturned".
Police said the latest package explosion was reported in the 6700 block of Galindo Street, near East Riverside Drive and Montopolis Drive, just before noon. "They brought that package inside the residence and as they opened that package, both victims were in the kitchen and the package exploded causing the injuries that resulted in the young man's death and the injuries to the adult female".
Austin Police Chief Brian Manley warned residents to avoid opening unexpected packages.
Monday's first blast happened at a home in Springdale Hills, a leafy neighborhood of houses mostly from the 1960s and 1970s.
"Our advice at this point is that if you get a package from someone that you don't know who it is, if it doesn't look like it's from a company but a random package, do not open it, call us and let us look at it", McManus said.
"Enjoy yourself. Have a good time", he said. The woman, in her 40s, was taken to an area hospital with injuries that were not thought to be life-threatening.
"This is the third in what we believe to be related incidents over the past 10 days", Manley said while briefing reporters near the site of Monday's second explosion.
A second explosion later in the morning left an elderly woman in critical condition after she was injured picking up a package in front of her home, police said. Along with a first explosion on March 2nd, which killed a man just north of Austin, CNN reports the authorities are now trying to determine whether or not all three incidents are connected.
Police Chief Brian Manley said Monday that investigators hope to collect surveillance video from nearby homes to identify a suspect.
Manley noted that authorities do not believe the packages were sent "by any of the official mail delivery services", saying that these "box-type deliveries" instead appeared to have been left on the victims' doorsteps overnight. Investigators said it was possible that the victims were targeted due to their race.
In a tweet Monday, organizers said, "SXSW is heartbroken by the explosions in Austin" and asked the thousands of festival attendees to notify the authorities of anything suspicious. A 17-year-old found a package in front of his front door. Despite similarities, police have not said if the two cases are related.
Special Agent Michelle Lee, a San Antonio-based spokesman for the FBI, said the agency responded to both events and was assisting Austin police, who were leading the local investigation.
Austin Mayor Steve Adler, speaking Monday at a news conference, said, "This is still a safe city".