CHILLICOTHE, Ohio (WCMH) -- The head of the state prisons department is speaking out about what she called a brutal murder of a guard on Christmas day Authorities say corrections officer Andrew Lansing was attacked and killed by 27-year-old inmate Rashawn Cannon.  Annette Chambers-Smith, the Director of the Ohio Department of Rehabilitation and Correction, did not specify how Officer Lansing was attacked but said this information would come out during the investigation.  She did confirm this is not the first time Officer Lansing has had a conflict with his accused killer, Cannon. Records show Cannon was convicted on felonious assault charges last year. He had been at the Ross County facility for just over a year. Chambers-Smith said in April Officer Lansing wrote a conduct report against Cannon. The conduct report had three charges on it; those were disrespect threats and disobedience to a direct order. Director Chambers-Smith said Cannon was found guilty of two of those - she did not specify which. NBC4 asked her if this attack could have been in retaliation to that conduct report. She was not able to give many more details about this but said they are looking into the history and gathering more information.  She said Ross Correctional Institution is a high-security facility. Incident reports say the attack happened while Lansing was in the guard shack which the director described as a shelter structure on the yard portion of the prison. “Andy Lansing elected to work voluntary overtime so that other people didn’t have to and could have Christmas off. That's what he was doing there," Chambers-Smith said. “Cannon's unit was released to go to the dining hall which is why he was on the yard. He veered away from going to the dining hall and instead went to where Officer Lansing was working and attacked him brutally.” Thursday, the union representing corrections officers sent a letter to Governor DeWine asking him to address issues inside the facility. One of those concerns was staffing shortages. NBC4 asked Director Chambers-Smith about the shortages and if that had anything to do with the incident. She said the Ross County facility currently has about an eleven percent vacancy rate among guards and staff. This equals about forty open positions. Ohio parents of children with disabilities sue state She said much of that has to do with new positions recently added for death row and security. Nineteen people have start dates for that prison between now and January 21. She said statewide the vacancy rate is 8 percent. “Regarding staffing, every post that was supposed to be filled that day was filled. How it compares to their normal schedule I don't have that detail but I can tell you I've been in contact with the warden regarding this matter and he did let me know they did start their shift with all their staff they were supposed to have and I think that was because like 8 people volunteered to work overtime,” Chambers-Smith said. Chambers-Smith said she has never heard anyone say a negative thing about Officer Lansing.  “Officer Lansing was pure, good, and solid. He always trained new staff and was a professional. He was a father, he was a husband and all he was trying to do was his job,” said Chambers-Smith.  The Ohio State Highway Patrol is investigating this incident.