Brower said the message said a "fortress-type wall" was to be erected around the meetinghouse.
"I'm 100 percent sure that wall isn't being built without Warren Jeffs' expressed orders," Brower said.
Jeffs is the president of the FLDS and is serving a sentence in Texas of life plus 20 years for crimes related to taking underage girls as wives. His brother, Lyle Jeffs, is the bishop of Colorado City and adjoining Hildale, Utah — also known as Short Creek — and runs the day-to-day operations of the FLDS.
Lyle Jeffs' legal wife recently filed for divorce and is prepared to testify in the U.S. Department of Justice's lawsuit against the Colorado City and Hildale town governments.
"I've got a feeling that Lyle is just completely paranoid about his legal wife," Brower said.
The construction also coincides with a Fourth of July celebration planned for Saturday at Cottonwood Park — one block northwest of the meetinghouse. The celebration organizers are former Jeffs followers.
It is thought to be the first community-wide celebration in Short Creek since Warren Jeffs took control in 2002.
Helaman Barlow, a former marshal in the two towns who has since testified about misdeeds he perpetrated on behalf of the FLDS, said Thursday he watched some of the construction and saw an excavator with "Twin City Water Works" written on the side.
That's the water utility that the Utah Attorney General's Office wants dissolved and placed in a receivership. A judge is considering the request. A Justice Department accountant's report says $1.7 million of Twin City Water proceeds were diverted to the FLDS and its members from 2004 through 2013.
Barlow believes the wall is a response to the July Fourth celebration. He said the Jeffs family is probably worried the celebration will spill into the meetinghouse parking lot and the faithful will be able to hear the music.
"The way the Jeffs boys work is, everything has to be a big threat to unite their people," Barlow said.
As many as 2,500 former Jeffs followers and their families are expected to attend the July Fourth festivities. Barlow owns a print shop and said he has spent two weeks making patriotic banners and signs for businesses that will have booths in Cottonwood Park.
The meetinghouse, known to people in Short Creek as simply "The LSJ," was constructed in 1986, according to tax records. It is where the FLDS hold their worship services.
In 2013, it also was revealed that the LSJ contained a control room where church security monitored a network of video cameras on public and private property so they knew who was entering the towns and who was talking to whom.