A convicted killer attacked a prison officer and tried to choke him as he was left out of his cell.
Prisoner Darren Wynne (21) from Ballyroe, Athy, Co Kildare, assaulted the assistant chief officer on the C1 landing in Portlaoise Prison at 7pm on Thursday night.
Witnesses reported that when Wynne's cell door was opened he grabbed the officer and put him in a headlock, trying to choke him.
"The two of them ended up on the ground and other prison staff had to intervene to separate them," a source told the Herald.
Another officer was also reported to have been injured as he came to the first officer's aid.
A prison source has said the attack by Wynne on the prison officer has been reported to gardai and is being treated as an assault.
The prison officer went to hospital for a check-up after the attack, but is not believed to be seriously hurt.
Wynne is also likely to face sanctions, such as loss of recreation time and remission from prison management.
Wynne is serving life imprisonment for the murder of his best friend in Co Kildare in 2013.
He has since been handed a 12-year sentence for firearms offences.
He was convicted of murdering Jamie Lindsay (20) at Coney Green, Coneyboro, Athy on April 6, 2013. The court heard that Lindsay was shot in the right eye at almost point blank range.
Wynne told gardai that his victim was threatening him over €1,000 for cannabis herb that had gone missing.
He said he also threatened to rape his grandmother and burn his house down.
Wynne was later also convicted of possession of a sawn-off shotgun and ammunition with intent to endanger life on the same occasion.
It was for this offence that he was later sentenced to 12 years.
Wynne had pleaded guilty to possession of a sawn-off shotgun and cartridges in suspicious circumstances and was sentenced to eight years for that offence. Mr Justice Sheehan suspended the final two years of each sentence provided that Wynne complies with his sentence management programme and backdated them to April, 12, 2013 for time spent in custody.
Both sentences are running concurrently.