Passage: Officers opened negotiations for surrender but Johnson said he would speak to black police officers only. Johnson stated that he had acted alone and was not part of any group. According to Chief Brown, Johnson appeared delusional during his standoff; "We had negotiated with him for about two hours, and he just basically lied to us, playing games, laughing at us, singing, asking how many did he get and that he wanted to kill some more." By about 2:30 a.m., Chief Brown saw no possibility of negotiating further and made the decision to use a bomb disposal remote control vehicle armed with about 1 pound (0.45 kilograms) of C-4 explosive. The plan was to move the robot to a point against a wall facing Johnson and then detonate the explosives. The robot exploded as intended, killing Johnson immediately. The robot, while sustaining damage to its extended arm, was still functional.It was later discovered that Johnson scrawled the letters "RB" in his own blood while in the college, apparently after being wounded while making his way up a stairwell. The meaning of "RB" and other markings made by Johnson was unclear, and investigators subsequently attempted to discern its meaning.Chief Brown said that during negotiations, Johnson declared he had placed explosives in downtown Dallas. A sweep of downtown Dallas found no presence of explosives.

Question: What did Johnson state?
he had acted alone and was not part of any group.