It reached a point where Tonner decided to slip out of town when citizens started talking about taking justice into their own hands.
The cause of all this was water - then, just like today, the lifeblood of the Inland Valley.
Depending on who you believed, Tonner was either a victim of a misunderstanding or the mastermind of a plot to hold hostage the water rights of most Pomona landowners.
The Irish-born Tonner was the lawyer for Lugarda Palomares, widow of Francisco Palomares, whose family had owned part of Rancho San Jose in far eastern Los Angeles County.
Following the breakup of the Mexican rancho system after California became a state, there were significant court fights over these lands.
One court ruling produced a question on the titles of about 2,000 acres sold by the Palomares family to Pomona-area settlers.
In dispute was whether water rights actually went with each sale of land - which everyone had assumed they did.
The Spanish-speaking Tonner claimed Lugarda Palomares had instructed him to offer the disputed water rights to each landowner at whatever price he felt appropriate. This purchase at up to $150 an acre would insure the cloud on their title be lifted, he said. She would later deny having given him these instructions.
During this period, Tonner transferred some titles to water rights out of state to a relative of Dr. B.S. Nichols, one of Tonner's cohorts. This was presumably done so residents couldn't take legal action against him in local courts, but would be forced to take their case to federal court.
It wasn't until early November 1891, when letters written by resident John E. Packard appeared in Pomona's two weekly newspapers, that the city really understood what was going on.
More than 500 angry Pomonans attended a mass meeting a few days later where charges and threats were thrown about. Committees were appointed to fight what they felt was a great injustice.
"The community has fully waked up to the great damage being done by this cloud on the titles to land covering a large part of the valley," wrote the Pomona Weekly Times of Nov. 7.
The battle that ensued was watched with interest from afar. The Los Angeles Times on Nov. 10 wrote about "Tonner's Peril and His Crime Against Citizens of Pomona." Newspapers as far away as San Francisco carried stories about Pomona's water war.
The atmosphere got a lot hotter when residents discovered Tonner's strategic retreat out of town.
Tonner in the Nov. 11 Los Angeles Times said he decided to disappear "because I was advised that I was in personal danger if I remained.
"I did not want to do anything that would increase the excitement, even if I could have had a guarantee of personal safety."
Unable to find Tonner, the angry residents turned to Mrs. Palomares at her north San Diego County home, demanding an explanation.
With son Frank interpreting (she spoke no English), she told the committee that she had no idea Tonner was using her authority in this way. She thought she had instructed him to sell some small, oddly shaped plots of land in Pomona.
She assured all the landowners that she would renounce any authority given to Tonner and would see that each landowner got clear title to his or her land.
In the last mass meeting, Dec. 26, about 150 landowners rejoiced over the end of the threat to their lands. Among the resolutions they composed praising Mrs. Palomares and themselves for a successful end to the crisis was one negative note:
"Resolved that we believe it would be for the best interests of Pomona and vicinity for P.C. Tonner and B.S. Nichols to remove the shame and disgrace forced upon us by their residence among us."
Or in other words, leave.
Tonner nevertheless returned to Pomona for the next eight years until his death in early 1900. And it seemed that time healed the wounds from this water battle.
His obituary offers no mention of the water scheme. Instead, it told of his work as a lawyer and teacher and his positive contributions to the community.
"Those who knew him most intimately say the kindest and best things of him," read the obituary.
Tonner is buried in the Palomares Cemetery on Towne Avenue with many other early Pomona residents.
Joe Blackstock writes on Inland Valley history every other Saturday. He can be reached by e-mail at firstname.lastname@example.org or by calling 909-483-9382.