A series of bombings that have shaken the lively and popular Texan city of Austin could be a “trial run” for a bigger attack, a former FBI adviser believes, as police in the state urgently hunt for clues amid fears of further blasts.
President Donald Trump called the perpetrator "sick" and said all resources were being devoted to tracking the person down.
"The bombings in Austin are terrible," he said.
"This is obviously a very sick individual, or individuals. And we’ll get to the bottom of it. It’s absolutely disgraceful. These are sick people and we have to find them as soon as possible."
APD responded to 420 suspicious package calls between 8 a.m. yesterday and 8 a.m. today bringing the total number to 1,257 calls since approximately 8 a.m. on March 12.— Austin Police Dept (@Austin_Police) March 20, 2018
Austin authorities said emergency personnel were responding to another reported explosion on Tuesday evening, this one at a Goodwill store in the southern part of the city.
Austin-Travis County EMS tweeted on Tuesday evening that at least one person was injured. Austin Police later tweeted that it was "an incendiary device", rather than a bomb. "We have no reason to believe this incident is related to previous package bombs," they added.
The incident had raised fears of a sixth explosion in the Austin area since March 2. So far, two people have been killed and four others seriously wounded.
FINAL Multiple assets #ATCEMS@AustinFireInfo@Austin_Police on scene Brodie Ln/W Slaughter Ln (1902) reported explosion: #ATCEMSMedics transported ~30s male with potentially serious, not expected to be life threatening, injuries to St Davids South Austin. No further info avail.— ATCEMS (@ATCEMS) March 21, 2018
The blast came after a FedEx employee was left with a ringing in the ears when a package exploded at a distribution centre in San Antonio, 80 miles south of Austin, in the early hours of Tuesday.
Brian Manley, chief of police for Austin, said the package that exploded in the San Antonio suburb of Schertz was bound for Austin.
William McManus, chief of police for San Antonio, said a second suspicious package was located at the Schertz facility later on Tuesday morning. It has been removed from the facility for further investigation.
And hours after the FedEx explosion in San Antonio, police were called to a FedEx site in Austin after reports of a suspicious package.
The fire department tweeted that a hazardous materials investigation was underway.
Michelle Lee, FBI spokesman for San Antonio, said they were linking the FedEx explosion to the other four Austin bombs this month.
"It would be silly for us not to admit that we suspect it’s related,” she said.
Hundreds of officers from multiple law enforcement agencies are now working on the case, amid fears that as time passes the person or people behind the explosions will seek more than just the thrill of the crimes themselves and will desire more recognition.
Randall Rogan, a Wake Forest University professor who is an expert on forensic linguistic analysis said he thought the perpetrator could soon make contact with police or release some sort of communiqué or manifesto.
Mr Rogan worked with the FBI on the Unabomber case, which saw three people killed between 1978 and 1995 in a nationwide bombing campaign targeting those involved with modern technology.
Mr Rogan said the new complexity of the fourth bombing, triggered with a tripwire on Sunday, might suggest it was a test for something even bigger.
"This is an increase and expansion of sophistication and most likely a trial run for something to come in the future," he said.
Robert Taylor, a former police detective who is now a criminologist at the University of Texas at Dallas, said eventually there will be a break in the case, but how long it will take remains to be seen.
"Something will come up somewhere. It will be a fingerprint on an envelope or DNA from saliva or a unique kind of detonator, or someone will just blab in a bar," he said.
Brian Manley, the chief of police for Austin, has offered a $115,000 reward for information and said they also believe the four attacks in Austin were all connected.
"Clearly we are dealing with a serial bomber,” he said, and issued a plea to the perpetrator.
"We assure you, we are listening and we want to understand what brought you to this point, and we want to listen to you, so please call us."
Indeed, authorities are at a loss to understand the motive behind the bombings, which killed two members of the same predominately black church – Anthony House, 39, who died on March 2 when he picked up a package on the front porch of his home, and 17-year-old Draylen Mason, who died ten days later.
On the same day as Mason was killed, a 75-year-old Hispanic woman picked up a package on her front porch when it exploded, seriously injuring her.
At first police believed the motive was racial hatred, but that changed on Sunday with the fourth bomb, possibly set off by a tripwire, injured two white male cyclists in their 20s.
Tens of thousands of residents received warnings to stay in their homes on Sunday night, which set the already-jittery city further on edge. Police then said there had been a glitch in the system, and the warning should only have gone to an area of 1,300 homes in the immediate vicinity of the bomb, rather than the majority of the city.
“I’m even afraid to check my mailbox,” said Tracy Nguyen, 32, who lives on the same street as the first bombing. “It seems like such a random act.”
Ms Nguyen, who is Vietnamese, said she was worried after hearing the attacks could be racially motivated.
“It could have been me,” she told the Austin American Statesman. “It could have been anyone.”
The bombings have cast a shadow over the annual South by Southwest festival of media and music, which drew to a close on Sunday having brought 300,000 people to the city to hear talks from Sadiq Khan and Elon Musk and hear music from the likes of Pussy Riot.
A bomb threat at the festival on Saturday evening caused the cancellation of a concert by the popular hip-hop band The Roots. A 26-year-old man was arrested on charges of making a terroristic threat in connection with that incident, but authorities did not link him to the explosions, and no device was found.
Austin has gained national attention for its technology startups and is one of the country’s fastest-growing metropolitan areas — which may make it more of a target.
But residents are left scratching their heads – and scared.
“I’m honestly scared to walk anywhere around Austin now,” Andres Vecchio wrote on Twitter. If these serial bombings were meant to incite terror, they’re definitely working.”
Amelia Tyler, who lives about a mile from Sunday’s explosion site, served in Iraq for two years with the Army Reserve and said it reminded her of the war zone.
“The randomness is so scary,” she said. “Bomb blasts are horrible, and no one should experience that.”
Steve Adler, mayor of Austin, told his local newspaper that he is trying to strike a balance between urging residents to be cautious while requesting that they remain calm and continue daily life.
“We are going to find out who did this, and we are going to stop it,” he said.