A serial bomber is menacing Austin, Texas, and now may be expanding his range.

Overnight, another bomb exploded inside a FedEx facility near San Antonio. The FBI suspects it may be linked to the previous four. No injuries have been reported in the FedEx explosion.

Sunday night, the fourth bomb in less than three weeks exploded in a residential area southwest of downtown Austin.

RELATED: Serial bomber is killing Texas residents with exploding packages

The previous three bombs were all disguised as packages delivered to specific houses. This time, the bomb was attached to a “For Sale” sign and rigged with a tripwire. Two men walking through the neighborhood apparently struck the tripwire and both were seriously injured in the blast.

Police say they see “similarities” in the bombs that make them believe the same killer is responsible. The tripwire bomb reveals a higher level of sophistication and skill, so investigators now believe the bomb-maker may have military or police explosive ordnance training.

Investigators are stumped because a serial bomber typically makes a device the same way each time, but that’s not happening in this case. They’re also surprised there haven’t been any demands or indication of motive from the perpetrator.

Police are urging the killer to communicate with them and have raised the reward to $115,000 for any information leading to an arrest.

“Sunday’s explosion largely sinks the hate crime theory.”

Oddly, the fourth bomb actually helps investigators because of the increasing amount of trace evidence left after the explosions. Surveillance video is expected to help crack the case since the bomber is personally delivering and setting up the devices.

When the second and third bombs exploded last week, several outlets, including CNN and the Washington Post seemed eager to pounce on the idea that this was a hate crime, since two black men were killed and an elderly Hispanic woman seriously injured. The Post even questioned whether there would have been more urgency to find the killer had the initial bomb gone off in an affluent, white neighborhood.

But Sunday’s explosion largely sinks the hate crime theory, since it was rigged to kill anyone who happened by. For the record, the two men injured by Sunday’s bomb were white.

When you’re dealing with a serial killer like this though, does the idea that it might be racially-motivated make it any more evil? It’s just evil, period.

Isn’t every murder essentially a “hate” crime?

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