Authorities had not previously disclosed details of the mobile phone video in which Mark Conditt admitted being behind the string of bombings that began on March 2, killing two people and wounding five others, beyond saying that it showed a troubled young man.
“I think the best evidence we have at this point in time is the confession itself … He did refer to himself as a psychopath,” US Republican Michael McCaul told a news conference in Austin.
“He did not show any remorse, in fact questioning himself for why he didn’t feel any remorse for what he did.
“It’s hard to imagine someone whose mind is so sick that they could commit bombings like this and feel absolutely no remorse,” he said.
Mr McCaul said there did not appear to be anything in Conditt’s confession “that was sort of racially motivated, but I know that is still part of the ongoing investigation”.
The first several bombing victims, including the two who died, were either African-American or Hispanic.
Federal investigators have been hunting clues about what drove Conditt, who was unemployed and lived with roommates in the Austin suburb of Pflugerville.
They also want to know whether he had help building or planting the bombs.
Three of the devices were left as parcels outside victims’ homes, while another was placed on a sidewalkand attached to a trip-wire mechanism.
Two more were shipped as FedEx parcels, which helped investigators unmask the bomber’s identity.
The second and third bombs went off while the Texas state capital was hosting its annual South by Southwest music, movies and tech festival, which draws about half a million people.
Conditt died after detonating an explosive device early on Wednesday as police ran toward his vehicle in an Austin suburb.