Austin bomber Mark Anthony Conditt left behind a 25-minute videotaped confession, detailing how he made six different explosives – but gave no clear motive behind his three-week reign of terror, authorities said Wednesday.

All the bombs are accounted for, with the final device being the one Conditt detonated on himself as cops were about to arrest him, officials said.

“We have at this point located a recording that the suspect in this incident made. It is about 25-minute recording where he talks about what he has done,” Austin police chief Brian Manley told reporters.

“I would classify this as a confession.”

Conditt’s videotaped mea culpa was left on a phone that cops found on him, according to Manley.

The 24-year-old Conditt was killed after police closed in on him at 4:57 a.m. Wednesday in Round Rock, Texas, about 20 miles north of Austin city limits.

“On this recording, the suspect describes the six bombs that he constructed with the level of specificity that he identified the differences among those six bombs,” Manley said.

“We can account for each and every one one of (the bombs).”

Conditt made the tape between 9 p.m. and 11 p.m. on Tuesday night and knew cops were closing in on him, police said.

While Conditt gave details on how he made the bombs, the killer didn’t say why he did it.

Austin’s top cop stopped short of calling Conditt’s bombings a racially motivated hate crime or the work of a politically motivated terrorist.

“I know everybody is interested in a motive and understanding why, and we are never going to be able to put a (rationale) behind these acts,” Manley said.

“But what I can tell you having listened to that recording, he does not at all mention anything about terrorism nor did he mention anything about hate. But instead, it is the outcry of a very challenged young man, talking about challenges in his personal life that led him to this point.”

Conditt was responsible for five bombings that killed two people and badly wounded four others since March 2, police said.