A homemade pipe bomb exploded and destroyed the marked car of a Salt Lake County sheriff's sergeant early Tuesday while the vehicle was parked in the driveway of his home.

Investigators say they fear the unknown bomber may have something against law enforcement officers and may strike again.A note found next to the vehicle said, "Be aware" and "You've not seen and heard the last of us," said Salt Lake County Sheriff Aaron Kennard. There were other messages on the note, but he said they don't make a lot of sense.

"I'm at a loss as to why and what," Kennard said. "I guess we, the police, are going to be the targets of some more stuff."

The 6- to 8-inch pipe bomb is believed to have been taped to the catalytic converter underneath Sgt. Bill Bills' patrol car. The sergeant and his wife heard a loud explosion about 1 a.m. They looked outside, saw nothing and decided to go back to bed, Kennard said. But moments later, Bills' wife looked outside again and saw the vehicle engulfed in flames.

Firefighters responded to 1295 E. 6600 South and doused the burning vehicle. Several pieces of the bomb had been embedded in the side of the house from the explosion. No one was injured, however.

"That thing could have been ugly. If the bomb had been placed underneath the gas tank it could have engulfed the home and done a number on Sgt. Bills, his wife and their baby boy," the sheriff said.

The device was probably a black-powder pipe bomb with a fuse. Kennard said the bomber would have had to crawl along a fence on the south side of Bills' property in order to light the bomb and then run away.

Bomb experts and arson investigators - including agents from the Bureau of Alcohol Tobacco and Firearms - continued to scour the scene of the bombing Thursday.

Provo Police Detective Richard Healey said the bombing is not likely related to the three recent pipe bombings that have occurred in Utah County. A suspect in that case was arrested at 3 a.m. Thursday, but he had been under surveillance since about 9 p.m. Wednesday.

The sheriff said there could be dozens of possible motives why the bomber may be after law enforcement officers - or Bills specifically - but he doesn't know what those motives are. He may be upset because of the recent Los Angeles police brutality, the recent killing of a West Valley man by a West Valley officer, or Kennard's Wednesday announcement of one of the largest gambling busts in Utah's history.

"There are endless possibilities," he said. "It puts me on notice. And it scares me (because) I'm concerned for the welfare of my people."

Bills is the patrol sergeant for the east side of Salt Lake County. The sheriff said he has been harassed in the past with obscene phone calls and vandalism. Because of its location near I-215, his home is a visible target because he parks his patrol car in the driveway.