That's over: The person who sent two suspicious envelopes to Maryland government buildings was a "lone wolf," an overzealous citizen angry about a highway sign that advertised the state's terrorism tip line. The envelope sent to Maryland's Democratic governor incinerated when someone in the state mailroom opened it, singeing the person's fingers. The envelope produced "a puff of smoke and a sulphur-type smell, like if you would strike a match." About 15 minutes later, a similar envelope was opened at a building 20 miles away. No explosives were found, only a letter explaining the sender's grievance with the highway sign, which urged drivers to report suspicious sightings. "Somebody doesn't like seeing that sign," Gov. Martin O'Malley said. State mailroom workers are expected to be back to work Friday.