A wave of deadly bombings in the capital city of Texas has escalated to a new level, after a fourth bomb exploded late Sunday night. Austin police stated in a press conference Monday that this latest bomb changes the whole picture, and they now are certain they are dealing with a serial bomber.

In the first three bombings, packages were left on individual properties, in which two people were killed and two injured. Since all the victims were African American, police had indicated it could be racially motivated.

However, Sunday night’s bomb was left along a street, and connected to a trip wire, indicating a much higher level of sophistication than the package bombs used in the first three attacks, police said.

Two white males, ages 22 and 23, were seriously injured in Sunday night’s attack, are are still hospitalized.

Police are asking people in the area who have surveillance cameras to turn their footage over to police so it can be examined, and have warned people to not touch any suspicious-looking packages.

“We are clearly dealing with what we believe to be a serial bomber at this point, based on the similarities between now what is the fourth device” and the previous ones, Police Chief Brian Manley said at Monday’s press briefing.

The Associated Press reported:

“Is this terrorism? Is this hate-related?” Manley asked. He said investigators will “have to determine if we see a specific ideology behind this.”

The police chief said the tripwire meant it was a more sophisticated device requiring a higher level of skill to construct than the previous bombs. He said the bombing represents a “significant change,” in that the earlier bombings appeared targeted, while the latest one would have hurt any random person walking by.

For days, police have been warning people not to touch unexpected or suspicious-looking packages, a chilling thought at a time when people get more doorstep deliveries than ever before because of the rise of online shopping. With the latest bombing, the attacks took on an even more sinister cast.

“With this tripwire, this changes things. It’s more sophisticated. It’s not targeted to individuals,” said FBI agent Chris Combs, in charge of the bureau’s San Antonio division. “We’re very concerned that with tripwires a child could be walking down a sidewalk and hit something.”

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