(STMW) — A botanist pleaded guilty Thursday to sending letters threatening to kill Chicago Police officers and their families soon after cops fatally shot a wild cougar in Roscoe Village.

Rich Hyerczyk, 54, pleaded guilty in federal court that he sent 90 threatening letters over nine-year period starting in 2003 — including one in which he threatened to burn down former Mayor Richard M. Daley’s vacation home in Michigan, the Sun-Times is reporting.

READ MORE: Chicago Weather: Rounding Out The Warmest Weekend Of The Winter

Charges against Hyerczyk were filed last week in a criminal information; on Thursday afternoon he appeared in court and pleaded guilty to one charge as part of a larger agreement.

The cougar’s death made front page news and sparked a lively public debate about whether police were right to shoot it.

Police at the time said they beefed up patrols around a North Side elementary school following a threatening letter — apparently from someone angry about the shooting of the young male cougar in the neighborhood.

The principal of the Audubon Elementary at 3500 N. Hoyne sent out a note to parents four days after Hyerczyk allegedly mailed his letter, letting them know police brought the letter to the school’s attention and “it appears to have been written by someone angry about the shooting of the cougar.”

The incident was about a block south of the school.

Police brass and then-Mayor Daley both defended the decision to shoot at the time.

In the aftermath of the shooting, another letter contained threats to torch the mayor’s Michigan summer home in retaliation for the killing, sources said at the time.

Though there’s no allegation in court papers that Hyerczyk sent that letter, the unidentified author was suspected of sending another threatening letter to Brookfield Zoo in 2003, sources said at the time.

On April 24, two days after the letter arrived, a fire that started near Daley’s Michigan house destroyed a neighbor’s multimillion-dollar home on Lake Michigan but spared the mayor’s retreat. Police said the fire was intentionally set.

READ MORE: MISSING: Khoshaba Dikyanos, 84, Last Seen In Lincoln Square

In November 2003, an envelope containing white powder and a letter containing numerous threats was delivered to Brookfield Zoo. The anonymous writer was angry about a wolf that was shot to death at the zoo earlier that month, authorities said.

Authorities said the cougar was the first seen in Cook County since at least 1855.

It may have started its life nearly 1,000 miles away in South Dakota. And the big cat definitely passed through southern Wisconsin as it wandered toward Chicago.

DNA testing showed the cat was same animal that was chased out of an abandoned barn near Milton, Wis., three months earlier, Cook County officials said at the time.

The DNA results also ruled out the possibility the cougar was an escaped exotic pet, officials said.

The cat was shot six times after being cornered by police near Audubon Elementary. It died of gunshot wounds to the heart and aorta, a necropsy concluded.

According to a biography posted on the Chicago Botanic Garden website, Hyerczyk is a graduate of St. Xavier University.

He has taught “natural history and botany classes at The Field Museum, the Morton Arboretum, and several Chicago-area park districts,” and is an expert on lichens who founded the Chicago Lichenological Society.

Calls to Hyerczyk’s Southwest Side home were not answered Thursday morning. His phone message contained only the sound of dogs barking.

MORE NEWS: Chicago Speed Cameras To Start Issuing $35 Tickets To Drivers Going 6 MPH Over The Limit On Monday

(Source: Sun-Times Media Wire © Chicago Sun-Times 2014. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed.)