I read that report also but I thought it might have been a suicide.The one news report I saw yesterday said that there was an audible countdown saying that it was a bomb and would explode in 15 minutes. If true, that’d lend credence to the idea that they only wanted to do property damage, not injure or kill people.
There was a spate of cases overseas a few years ago, where suicidal people would rent a hotel room and then mix chemicals to make a deadly poison to off themselves, after putting a note on the door warning first responders of the danger.