The gunman who killed five co-workers at the Molson Coors Brewery in Milwaukee last week came to work one day in 2015 to find out that a noose had been placed on his locker, the company disclosed Tuesday.

Police have not said what might have sparked the rampage by 51-year-old electrician Anthony Ferrill on Feb. 26, who died of an apparent self-inflicted gunshot wound.

The company said Ferrill never actually saw the racist symbol, as it was spotted and removed before he got to work, the company said.

“Our HR team brought it to his attention,” Adam Collins, chief communications and corporate affairs officer for Molson Coors, told reporters, according to NBC affiliate WTMJ in Milwaukee.

Collins said of the noose incident, “There aren’t words to describe that; it’s awful.”

An internal probe was conducted at the time, but it was unable to determine who was responsible, and Ferrill didn’t file a formal complaint about it, according to Collins.

“We investigated it fully and tried to find video cameras and whatnot that we have inside the space to see if we could figure out who placed it there,” he said.

A Milwaukee police spokeswoman said the department is aware of the noose incident, but declined to substantively discuss the matter.

Of the shooting, police Sgt. Sheronda Grant told NBC News on Wednesday, “It is still an open investigation,”

The employees killed by Ferrill were Dale Hudson, 60; Gennady Levshetz, 61; Jesus Valle Jr., 33; Dana Walk, 57; and Trevor Wetselaar, 33.

A representative for Mayor Tom Barrett could not immediately be reached for comment Wednesday.

State Sen. Lena Taylor, who is challenging Barrett in the race for mayor, said she believes it is possible that the 2015 incident could be connected to last week’s carnage.

“From what we’re hearing on the ground, and knowing Milwaukee’s racial climate, yes, there’s certainly a possibility that this incident may have been a motive in the shooting,” Taylor said in a statement.