Fear escalated across Texas' capital city on Monday after the fourth bombing this month - a blast that was triggered this time by a tripwire, demonstrating what police called a "higher level of sophistication" than the package bombs used in the previous attacks. They are now in stable condition at a local hospital, he said, but sustained "significant injuries". This time, the victim could have anybody, even a child, authorities said.
"This is something we see with serial offenders, serial killers, serial bombers, serial arsonists".
During the news conference, authorities also increased the reward amount to $115,000 for any information leading to the arrest of the suspect or suspects. Tripwires can be made from fishing line or a metal wire attached to the bomb.
"With this tripwire, this changes things", said Christopher Combs, special agent in charge of the FBI's San Antonio division.
"Given the darkness, we have not really had an opportunity to really look at this blast site to determine what has happened", the chief said. Two of the injuries occurred last night when a bomb went off in a residential neighborhood, possibly using a tripwire mechanism according to police.
Police haven't confirmed the latest explosion, which injured two men who were riding or pushing bikes, is related to the first three, but they're looking into the possibility.
'Again, airplanes go by and cars backfire so we didn't think much of it. Race could still be a factor in the bombings, he added. Manley said they are now in stable condition.
The three prior bombs were left as packages on doorsteps, while Manley said Sunday's device was different: It was placed on the side of the road. However, when they arrived, ATCEMS and Austin police said the explosion was actually in the 4800 block of Dawn Song Drive, which is one block away.
Since the fourth explosion took place in southwest Austin, the warning area has expanded, UTPD said in a statement.
"I will reach out to the suspect or suspects and ask that you contact us, ask that you reach out to us".
Manley said on Good Morning America that the victims of Sunday's explosion were white males, but added that no theory has been ruled out yet.
"This is a bomber that knows explosives", Burton said.
UTPD has also urged people to call 911 to report any suspicious items or people.
Investigators plan to scan the area for more clues as daylight hits the neighborhood, authorities said.
"We heard sirens just coming and coming", Stacy said.
"We're going to find out who is responsible for this and we're going to stop it", he said. Authorities later arrested a 26-year-old man, and the incident did not appear to be related to any previous explosions.
Hundreds of law enforcement officers have responded to the attacks.
He then said he wanted to tap into the psyche of the bomber or bombers. At this point we don't have any specifics leading us to one suspect. We assure you that we are listening.
It killed 17-year-old Draylen Mason, a promising student who played stand-up bass in a youth orchestra and was taking college classes while in high school.