In two of three final reports there are bombs worn or placed by the attackers. In two of the reports the final assault was started by government personell (either directly, letting it look like the hostage takers started it, or by killing the guy on a dead man’s switch). In one report it was classified as a suicide attack from the start.
The dead man’s switch was confirmed by one of the surviving attackers. He also was the one speaking of a dispute between the attackers concerning the target building (school vs. police station).